



RATS Working Group                                           H. Birkholz
Internet-Draft                                                  M. Eckel
Intended status: Standards Track                          Fraunhofer SIT
Expires: 19 November 2022                                    S. Bhandari
                                                             ThoughtSpot
                                                                 E. Voit
                                                               B. Sulzen
                                                                   Cisco
                                                                  L. Xia
                                                                  Huawei
                                                               T. Laffey
                                                                     HPE
                                                             G. Fedorkow
                                                                 Juniper
                                                             18 May 2022


   A YANG Data Model for Challenge-Response-based Remote Attestation
                         Procedures using TPMs
                   draft-ietf-rats-yang-tpm-charra-21

Abstract

   This document defines YANG RPCs and a few configuration nodes
   required to retrieve attestation evidence about integrity
   measurements from a device, following the operational context defined
   in TPM-based Network Device Remote Integrity Verification.
   Complementary measurement logs are also provided by the YANG RPCs,
   originating from one or more roots of trust for measurement (RTMs).
   The module defined requires at least one TPM 1.2 or TPM 2.0 as well
   as a corresponding TPM Software Stack (TSS), or equivalent hardware
   implementations that include the protected capabilities as provided
   by TPMs as well as a corresponding software stack, included in the
   device components of the composite device the YANG server is running
   on.

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 https://datatracker.ietf.org/drafts/current/.






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   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 19 November 2022.

Copyright Notice

   Copyright (c) 2022 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . .   3
   2.  The YANG Module for Basic Remote Attestation Procedures . . .   3
     2.1.  YANG Modules  . . . . . . . . . . . . . . . . . . . . . .   3
       2.1.1.  'ietf-tpm-remote-attestation' . . . . . . . . . . . .   4
       2.1.2.  'ietf-tcg-algs' . . . . . . . . . . . . . . . . . . .  33
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  48
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  49
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  51
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .  51
     5.2.  Informative References  . . . . . . . . . . . . . . . . .  56
   Appendix A.  Integrity Measurement Architecture (IMA) . . . . . .  56
   Appendix B.  IMA for Network Equipment Boot Logs  . . . . . . . .  57
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  58

1.  Introduction

   This document is based on the general terminology defined in the
   [I-D.ietf-rats-architecture] and uses the operational context defined
   in [I-D.ietf-rats-tpm-based-network-device-attest] as well as the
   interaction model and information elements defined in
   [I-D.ietf-rats-reference-interaction-models].  The currently
   supported hardware security modules (HSMs) are the Trusted Platform
   Modules (TPMs) [TPM1.2] and [TPM2.0] as specified by the Trusted
   Computing Group (TCG).  One TPM, or multiple TPMs in the case of a



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   Composite Device, are required in order to use the YANG module
   defined in this document.  Each TPM is used as a root of trust for
   storage (RTS) in order to store system security measurement Evidence.
   And each TPM is used as a root of trust for reporting (RTR) in order
   to retrieve attestation Evidence.  This is done by using a YANG RPC
   to request a quote which exposes a rolling hash of the security
   measurements held internally within the TPM.

   Specific terms imported from [I-D.ietf-rats-architecture] and used in
   this document include: Attester, Composite Device, Evidence.

   Specific terms imported from [TPM2.0-Key] and used in this document
   include: Endorsement Key (EK), Initial Attestation Key (IAK),
   Attestation Identity Key (AIK), Local Attestation Key (LAK).

1.1.  Requirements notation

   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.

2.  The YANG Module for Basic Remote Attestation Procedures

   One or more TPMs MUST be embedded in a Composite Device that provides
   attestation evidence via the YANG module defined in this document.
   The ietf-tpm-remote-attestation YANG module enables a composite
   device to take on the role of an Attester, in accordance with the
   Remote Attestation Procedures (RATS) architecture
   [I-D.ietf-rats-architecture], and the corresponding challenge-
   response interaction model defined in the
   [I-D.ietf-rats-reference-interaction-models] document.  A fresh nonce
   with an appropriate amount of entropy [NIST-915121] MUST be supplied
   by the YANG client in order to enable a proof-of-freshness with
   respect to the attestation Evidence provided by the Attester running
   the YANG datastore.  Further, this nonce is used to prevent replay
   attacks.  The method for communicating the relationship of each
   individual TPM to specific measured component within the Composite
   Device is out of the scope of this document.

2.1.  YANG Modules

   In this section the several YANG modules are defined.







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2.1.1.  'ietf-tpm-remote-attestation'

   This YANG module imports modules from [RFC6991] with prefix 'yang',
   [RFC8348] with prefix 'hw', [I-D.ietf-netconf-keystore] with prefix
   'ks', and 'ietf-tcg-algs.yang' Section 2.1.2.3 with prefix 'taa'.
   Additionally, references are made to [RFC8032], [RFC8017], [RFC6933],
   [TPM1.2-Commands], [TPM2.0-Arch], [TPM2.0-Structures], [TPM2.0-Key],
   [TPM1.2-Structures], [bios-log], [BIOS-Log-Event-Type], as well as
   Appendix A and Appendix B.

2.1.1.1.  Features

   This module supports the following features:

   *  'mtpm': Indicates that multiple TPMs on the device can support
      remote attestation.  For example, this feature could be used in
      cases where multiple line cards are present, each with its own
      TPM.

   *  'bios': Indicates that the device supports the retrieval of BIOS/
      UEFI event logs. [bios-log]

   *  'ima': Indicates that the device supports the retrieval of event
      logs from the Linux Integrity Measurement Architecture (IMA, see
      Appendix A).

   *  'netequip_boot': Indicates that the device supports the retrieval
      of netequip boot event logs.  See Appendix A and Appendix B.

2.1.1.2.  Identities

   This module supports the following types of attestation event logs:
   'bios', 'ima', and 'netequip_boot'.

2.1.1.3.  Remote Procedure Calls (RPCs)

   In the following, RPCs for both TPM 1.2 and TPM 2.0 attestation
   procedures are defined.

2.1.1.3.1.  'tpm12-challenge-response-attestation'

   This RPC allows a Verifier to request signed TPM PCRs (_TPM Quote_
   operation) from a TPM 1.2 compliant cryptoprocessor.  Where the
   feature 'mtpm' is active, and one or more 'certificate-name' is not
   provided, all TPM 1.2 compliant cryptoprocessors will respond.  A
   YANG tree diagram of this RPC is as follows:





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   +---x tpm12-challenge-response-attestation {taa:tpm12}?
     +---w input
     |  +---w tpm12-attestation-challenge
     |     +---w pcr-index*          pcr
     |     +---w nonce-value         binary
     |     +---w certificate-name*   certificate-name-ref
     |             {tpm:mtpm}?
     +--ro output
        +--ro tpm12-attestation-response* []
           +--ro certificate-name    certificate-name-ref
           +--ro up-time?            uint32
           +--ro TPM_QUOTE2?         binary

2.1.1.3.2.  'tpm20-challenge-response-attestation'

   This RPC allows a Verifier to request signed TPM PCRs (_TPM Quote_
   operation) from a TPM 2.0 compliant cryptoprocessor.  Where the
   feature 'mtpm' is active, and one or more 'certificate-name' is not
   provided, all TPM 2.0 compliant cryptoprocessors will respond.  A
   YANG tree diagram of this RPC is as follows:

   +---x tpm20-challenge-response-attestation {taa:tpm20}?
      +---w input
      |  +---w tpm20-attestation-challenge
      |     +---w nonce-value            binary
      |     +---w tpm20-pcr-selection* []
      |     |  +---w tpm20-hash-algo?   identityref
      |     |  +---w pcr-index*         pcr
      |     +---w certificate-name*      certificate-name-ref
      |             {tpm:mtpm}?
      +--ro output
         +--ro tpm20-attestation-response* []
            +--ro certificate-name       certificate-name-ref
            +--ro TPMS_QUOTE_INFO        binary
            +--ro quote-signature?       binary
            +--ro up-time?               uint32
            +--ro unsigned-pcr-values* []
               +--ro tpm20-hash-algo?   identityref
               +--ro pcr-values* [pcr-index]
                  +--ro pcr-index    pcr
                  +--ro pcr-value?   binary

   An example of an RPC challenge requesting PCRs 0-7 from a SHA-256
   bank could look like the following:







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 <rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
   <tpm20-challenge-response-attestation>
       xmlns="urn:ietf:params:xml:ns:yang:ietf-tpm-remote-attestation">
     <certificate-name>
       (identifier of a TPM signature key with which the Verifier is
       supposed to sign the attestation data)
     </certificate-name>
     <nonce>
       0xe041307208d9f78f5b1bbecd19e2d152ad49de2fc5a7d8dbf769f6b8ffdeab9
     </nonce>
     <tpm20-pcr-selection>
       <tpm20-hash-algo
           xmlns="urn:ietf:params:xml:ns:yang:ietf-tcg-algs">
         TPM_ALG_SHA256
       </tpm20-hash-algo>
       <pcr-index>0</pcr-index>
       <pcr-index>1</pcr-index>
       <pcr-index>2</pcr-index>
       <pcr-index>3</pcr-index>
       <pcr-index>4</pcr-index>
       <pcr-index>5</pcr-index>
       <pcr-index>6</pcr-index>
       <pcr-index>7</pcr-index>
     </tpm20-pcr-selection>
   </tpm20-challenge-response-attestation>
 </rpc>

   A successful response could be formatted as follows:

   <rpc-reply message-id="101"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <tpm20-attestation-response
       xmlns="urn:ietf:params:xml:ns:yang:ietf-tpm-remote-attestation">
       <certificate-name
           xmlns="urn:ietf:params:xml:ns:yang:ietf-keystore">
           (instance of Certificate name in the Keystore)
       </certificate-name>
       <attestation-data>
          (raw attestation data, i.e. the TPM quote; this includes
          a composite digest of requested PCRs, the nonce,
          and TPM 2.0 time information.)
       </attestation-data>
       <quote-signature>
           (signature over attestation-data using the TPM key
           identified by sig-key-id)
       </quote-signature>
     </tpm20-attestation-response>
   </rpc-reply>



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2.1.1.4.  'log-retrieval'

   This RPC allows a Verifier to acquire the evidence which was extended
   into specific TPM PCRs.  A YANG tree diagram of this RPC is as
   follows:

       +---x log-retrieval
          +---w input
          |  +---w log-type        identityref
          |  +---w log-selector* []
          |     +---w name*                      string
          |     +---w (index-type)?
          |     |  +--:(last-entry)
          |     |  |  +---w last-entry-value?    binary
          |     |  +--:(index)
          |     |  |  +---w last-index-number?   uint64
          |     |  +--:(timestamp)
          |     |     +---w timestamp?           yang:date-and-time
          |     +---w log-entry-quantity?        uint16
          +--ro output
             +--ro system-event-logs
                +--ro node-data* []
                   +--ro name?         string
                   +--ro up-time?      uint32
                   +--ro log-result
                      +--ro (attested_event_log_type)
                         +--:(bios) {bios}?
                         |  +--ro bios-event-logs
                         |     +--ro bios-event-entry* [event-number]
                         |        +--ro event-number    uint32
                         |        +--ro event-type?     uint32
                         |        +--ro pcr-index?      pcr
                         |        +--ro digest-list* []
                         |        |  +--ro hash-algo?   identityref
                         |        |  +--ro digest*      binary
                         |        +--ro event-size?     uint32
                         |        +--ro event-data*     binary
                         +--:(ima) {ima}?
                         |  +--ro ima-event-logs
                         |     +--ro ima-event-entry* [event-number]
                         |        +--ro event-number               uint64
                         |        +--ro ima-template?              string
                         |        +--ro filename-hint?             string
                         |        +--ro filedata-hash?             binary
                         |        +--ro filedata-hash-algorithm?   string
                         |        +--ro template-hash-algorithm?   string
                         |        +--ro template-hash?             binary
                         |        +--ro pcr-index?                 pcr



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                         |        +--ro signature?                 binary
                         +--:(netequip_boot) {netequip_boot}?
                            +--ro boot-event-logs
                               +--ro boot-event-entry* [event-number]
                                  +--ro event-number               uint64
                                  +--ro ima-template?              string
                                  +--ro filename-hint?             string
                                  +--ro filedata-hash?             binary
                                  +--ro filedata-hash-algorithm?   string
                                  +--ro template-hash-algorithm?   string
                                  +--ro template-hash?             binary
                                  +--ro pcr-index?                 pcr
                                  +--ro signature?                 binary

2.1.1.5.  Data Nodes

   This section provides a high level description of the data nodes
   containing the configuration and operational objects with the YANG
   model.  For more details, please see the YANG model itself in
   Figure 1.

   Container 'rats-support-structures':  This houses the set of
      information relating to remote attestation for a device.  This
      includes specific device TPM(s), the compute nodes (such as line
      cards) on which the TPM(s) reside, and the algorithms supported
      across the platform.

   Container 'tpms':  Provides configuration and operational details for
      each supported TPM, including the tpm-firmware-version, PCRs which
      may be quoted, certificates which are associated with that TPM,
      and the current operational status.  Of note are the certificates
      which are associated with that TPM.  As a certificate is
      associated with a particular TPM attestation key, knowledge of the
      certificate allows a specific TPM to be identified.

















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   +--rw tpms
      +--rw tpm* [name]
         +--rw name                string
         +--ro hardware-based      boolean
         +--ro physical-index?     int32 {hw:entity-mib}?
         +--ro path?               string
         +--ro compute-node        compute-node-ref {tpm:mtpm}?
         +--ro manufacturer?       string
         +--rw firmware-version    identityref
         +--rw tpm12-hash-algo?    identityref {taa:tpm12}?
         +--rw tpm12-pcrs*         pcr
         +--rw tpm20-pcr-bank* [tpm20-hash-algo]  {taa:tpm20}?
         |  +--rw tpm20-hash-algo    identityref
         |  +--rw pcr-index*         tpm:pcr
         +--ro status              enumeration
         +--rw certificates
            +--rw certificate* [name]
               +--rw name            string
               +--rw keystore-ref?   leafref {ks:asymmetric-keys}?
               +--rw type?           enumeration

   container 'attester-supported-algos' - Identifies which TCG hash
   algorithms are available for use on the Attesting platform.  An
   operator will use this information to limit algorithms available for
   use by RPCs to just a desired set from the universe of all allowed
   hash algorithms by the TCG.

        +--rw attester-supported-algos
           +--rw tpm12-asymmetric-signing*   identityref {taa:tpm12}?
           +--rw tpm12-hash*                 identityref {taa:tpm12}?
           +--rw tpm20-asymmetric-signing*   identityref {taa:tpm20}?
           +--rw tpm20-hash*                 identityref {taa:tpm20}?

   container 'compute-nodes' - When there is more than one TPM
   supported, this container maintains the set of information related to
   the compute node associated with a specific TPM.  This allows each
   specific TPM to identify to which 'compute-node' it belongs.

        +--rw compute-nodes {tpm:mtpm}?
           +--ro compute-node* [node-id]
              +--ro node-id                string
              +--ro node-physical-index?   int32 {hw:entity-mib}?
              +--ro node-name?             string
              +--ro node-location?         string

2.1.1.6.  YANG Module





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   <CODE BEGINS> file "ietf-tpm-remote-attestation@2022-05-17.yang"
   module ietf-tpm-remote-attestation {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-tpm-remote-attestation";
     prefix tpm;

     import ietf-yang-types {
       prefix yang;
     }
     import ietf-hardware {
       prefix hw;
     }
     import ietf-keystore {
       prefix ks;
     }
     import ietf-tcg-algs {
       prefix taa;
     }

     organization
       "IETF RATS (Remote ATtestation procedureS) Working Group";
     contact
       "WG Web  : <https://datatracker.ietf.org/wg/rats/>
        WG List : <mailto:rats@ietf.org>
        Author  : Eric Voit <evoit@cisco.com>
        Author  : Henk Birkholz <henk.birkholz@sit.fraunhofer.de>
        Author  : Michael Eckel <michael.eckel@sit.fraunhofer.de>
        Author  : Shwetha Bhandari <shwetha.bhandari@thoughtspot.com>
        Author  : Bill Sulzen <bsulzen@cisco.com>
        Author  : Liang Xia (Frank) <frank.xialiang@huawei.com>
        Author  : Tom Laffey <tom.laffey@hpe.com>
        Author  : Guy Fedorkow <gfedorkow@juniper.net>";
     description
       "A YANG module to enable a TPM 1.2 and TPM 2.0 based
        remote attestation procedure using a challenge-response
        interaction model and the TPM 1.2 and TPM 2.0 Quote
        primitive operations.

        Copyright (c) 2022 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 XXXX



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        (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 2022-05-17 {
       description
         "Initial version";
       reference
         "RFC XXXX: A YANG Data Model for Challenge-Response-based Remote
          Attestation Procedures using TPMs";
     }

     /*****************/
     /*   Features    */
     /*****************/

     feature mtpm {
       description
         "The device supports the remote attestation of multiple
          TPM based cryptoprocessors.";
     }

     feature bios {
       description
         "The device supports the bios logs.";
       reference
         "bios-log:
          https://trustedcomputinggroup.org/wp-content/uploads/
          PC-ClientSpecific_Platform_Profile_for_TPM_2p0_Systems_v51.pdf
          Section 9.4.5.2";
     }

     feature ima {
       description
         "The device supports Integrity Measurement Architecture logs.
          Many variants of IMA logs exist in the deployment.  Each encodes
          the log entry contents as the specific measurements which get
          hashed into a PCRs as Evidence.  See the reference below for
          one example of such an encoding.";
       reference
         "ima-log:
          https://www.trustedcomputinggroup.org/wp-content/uploads/
          TCG_IWG_CEL_v1_r0p41_pub.pdf  Section 5.1.6";



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     }

     feature netequip_boot {
       description
         "The device supports the netequip_boot logs.";
       reference
         "netequip-boot-log:
          RFC XXXX  Appendix B";
     }

     /*****************/
     /*   Typedefs    */
     /*****************/

     typedef pcr {
       type uint8 {
         range "0..31";
       }
       description
         "Valid index number for a PCR.  A {{TPM2.0}} compliant PCR index
          extends from 0-31.  At this time a typical TPM would have no
          more than 32 PCRS.";
     }

     typedef compute-node-ref {
       type leafref {
         path "/tpm:rats-support-structures/tpm:compute-nodes"
            + "/tpm:compute-node/tpm:node-id";
       }
       description
         "This type is used to reference a hardware node.  Note that an
          implementer might include an alternative leafref pointing to a
          different YANG module node specifying hardware structures.";
     }

     typedef certificate-name-ref {
       type leafref {
         path "/tpm:rats-support-structures/tpm:tpms/tpm:tpm"
            + "/tpm:certificates/tpm:certificate/tpm:name";
       }
       description
         "A type which allows identification of a TPM based certificate.";
     }

     /******************/
     /*   Identities   */
     /******************/




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     identity attested_event_log_type {
       description
         "Base identity allowing categorization of the reasons why an
          attested measurement has been taken on an Attester.";
     }

     identity ima {
       base attested_event_log_type;
       description
         "An event type recorded in IMA.";
     }

     identity bios {
       base attested_event_log_type;
       description
         "An event type associated with BIOS/UEFI.";
     }

     identity netequip_boot {
       base attested_event_log_type;
       description
         "An event type associated with Network Equipment Boot.";
     }

     /*****************/
     /*   Groupings   */
     /*****************/

     grouping tpm20-hash-algo {
       description
         "The cryptographic algorithm used to hash the TPM2 PCRs.  This
          must be from the list of platform supported options.";
       leaf tpm20-hash-algo {
         type identityref {
           base taa:hash;
         }
         must '. = /tpm:rats-support-structures'
            + '/tpm:attester-supported-algos/tpm:tpm20-hash' {
           error-message "This platform does not support tpm20-hash-algo";
         }
         description
           "The hash scheme that is used to hash a TPM2.0 PCR. This
            must be one of those supported by a platform.
            Where this object does not appear, the default value of
            'taa:TPM_ALG_SHA256' will apply.";
       }
     }




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     grouping tpm12-hash-algo {
       description
         "The cryptographic algorithm used to hash the TPM1.2 PCRs.";
       leaf tpm12-hash-algo {
         type identityref {
           base taa:hash;
         }
         must '. = /tpm:rats-support-structures'
            + '/tpm:attester-supported-algos/tpm:tpm12-hash' {
           error-message "This platform does not support tpm12-hash-algo";
         }
         description
           "The hash scheme that is used to hash a TPM1.2 PCR. This
            MUST be one of those supported by a platform.
            Where this object does not appear, the default value of
            'taa:TPM_ALG_SHA1' will apply.";
       }
     }

     grouping nonce {
       description
         "A random number intended to guarantee freshness and for use
          as part of a replay-detection mechanism.";
       leaf nonce-value {
         type binary;
         mandatory true;
         description
           "A cryptographically generated random number which should
            not be predictable prior to its issuance from a random
            number generation function. The random number MUST be
            derived from an entropy source external to the Attester.

            Note that a nonce sent into a TPM will typically be 160 or 256
            binary digits long.  (This is 20 or 32 bytes.) So if fewer
            binary digits are sent, this nonce object will be padded
            with leading zeros within Quotes returned from the TPM.
            Additionally if more bytes are sent, the nonce will be trimmed
            to the most significant binary digits.";
       }
     }

     grouping tpm12-pcr-selection {
       description
         "A Verifier can request one or more PCR values using its
          individually created Attestation Key Certificate (AC).
          The corresponding selection filter is represented in this
          grouping.";
       leaf-list pcr-index {



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         type pcr;
         description
           "The numbers/indexes of the PCRs. In addition, any selection
            of PCRs MUST verify that the set of PCRs requested are a
            subset the set of PCRs exposed by in the leaf-list
            /tpm:rats-support-structures
            /tpm:tpms/tpm:tpm[name=current()]/tpm:tpm12-pcrs";
       }
     }

     grouping tpm20-pcr-selection {
       description
         "A Verifier can acquire one or more PCR values, which are hashed
          together in a TPM2B_DIGEST coming from the TPM2.  The selection
          list of desired PCRs and the Hash Algorithm is represented in
          this grouping.";
       list tpm20-pcr-selection {
         unique "tpm20-hash-algo";
         description
           "Specifies the list of PCRs and Hash Algorithms that can be
            returned within a TPM2B_DIGEST.";
         reference
           "TPM2.0-Structures:
            https://www.trustedcomputinggroup.org/wp-content/uploads/
            TPM-Rev-2.0-Part-2-Structures-01.38.pdf  Section 10.9.7";
         uses tpm20-hash-algo;
         leaf-list pcr-index {
           type pcr;
           description
             "The numbers of the PCRs that which are being tracked
              with a hash based on the tpm20-hash-algo.  In addition,
              any selection of PCRs MUST verify that the set of PCRs
              requested are a subset the set of PCR indexes selected
              are available for that specific TPM.";
         }
       }
     }

     grouping certificate-name-ref {
       description
         "Identifies a certificate in a keystore.";
       leaf certificate-name {
         type certificate-name-ref;
         mandatory true;
         description
           "Identifies a certificate in a keystore.";
       }
     }



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     grouping tpm-name {
       description
         "A unique TPM on a device.";
       leaf name {
         type string;
         description
           "Unique system generated name for a TPM on a device.";
       }
     }

     grouping node-uptime {
       description
         "Uptime in seconds of the node.";
       leaf up-time {
         type uint32;
         description
           "Uptime in seconds of this node reporting its data";
       }
     }

     grouping tpm12-attestation {
       description
         "Contains an instance of TPM1.2 style signed cryptoprocessor
          measurements.  It is supplemented by unsigned Attester
          information.";
       uses node-uptime;
       leaf TPM_QUOTE2 {
         type binary;
         description
           "Result of a TPM1.2 Quote2 operation. This includes PCRs,
            signatures, locality, the provided nonce and other data which
            can be further parsed to appraise the Attester.";
         reference
           "TPM1.2-Commands:
            TPM1.2 commands rev116 July 2007, Section 16.5
            https://trustedcomputinggroup.org/wp-content/uploads
            /TPM-Main-Part-3-Commands_v1.2_rev116_01032011.pdf";
       }
     }

     grouping tpm20-attestation {
       description
         "Contains an instance of TPM2 style signed cryptoprocessor
          measurements.  It is supplemented by unsigned Attester
          information.";
       leaf TPMS_QUOTE_INFO {
         type binary;
         mandatory true;



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         description
           "A hash of the latest PCR values (and the hash algorithm used)
            which have been returned from a Verifier for the selected PCRs
            and Hash Algorithms.";
         reference
           "TPM2.0-Structures:
            https://www.trustedcomputinggroup.org/wp-content/uploads/
            TPM-Rev-2.0-Part-2-Structures-01.38.pdf  Section 10.12.1";
       }
       leaf quote-signature {
         type binary;
         description
           "Quote signature returned by TPM Quote.  The signature was
            generated using the key associated with the
            certificate 'name'.";
         reference
           "TPM2.0-Structures:
            https://www.trustedcomputinggroup.org/wp-content/uploads/
            TPM-Rev-2.0-Part-2-Structures-01.38.pdf  Section 11.2.1";
       }
       uses node-uptime;
       list unsigned-pcr-values {
         description
           "PCR values in each PCR bank. This might appear redundant with
            the TPM2B_DIGEST, but that digest is calculated across multiple
            PCRs.  Having to verify across multiple PCRs does not
            necessarily make it easy for a Verifier to appraise just the
            minimum set of PCR information which has changed since the last
            received TPM2B_DIGEST.  Put another way, why should a Verifier
            reconstruct the proper value of all PCR Quotes when only a
            single PCR has changed?
            To help this happen, if the Attester does know specific PCR
            values, the Attester can provide these individual values via
            'unsigned-pcr-values'.   By comparing this information to
            what has previously been validated, it is possible for a
            Verifier to confirm the Attester's signature while eliminating

            significant processing.  Note that there should never be a
            result where an unsigned PCR value differs from what may be
            reconstructed from the within the PCR quote and the event logs.
            If there is a difference, a signed result which has been
            verified from retrieved logs is considered definitive.";
         uses tpm20-hash-algo;
         list pcr-values {
           key "pcr-index";
           description
             "List of one PCR bank.";
           leaf pcr-index {



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             type pcr;
             description
               "PCR index number.";
           }
           leaf pcr-value {
             type binary;
             description
               "PCR value.";
             reference
               "TPM2.0-Structures:
                https://www.trustedcomputinggroup.org/wp-content/uploads/
                TPM-Rev-2.0-Part-2-Structures-01.38.pdf  Section 10.9.7";
           }
         }
       }
     }

     grouping log-identifier {
       description
         "Identifier for type of log to be retrieved.";
       leaf log-type {
         type identityref {
           base attested_event_log_type;
         }
         mandatory true;
         description
           "The corresponding measurement log type identity.";
       }
     }

     grouping boot-event-log {
       description
         "Defines a specific instance of an event log entry
          and corresponding to the information used to
          extend the PCR";
       leaf event-number {
         type uint32;
         description
           "Unique event number of this event which monotonically
            increases within a given event log.  The maximum event
            number should not be reached, nor is wrapping back to
            an earlier number supported.";
       }
       leaf event-type {
         type uint32;
         description
           "BIOS Log Event Type:
            https://trustedcomputinggroup.org/wp-content/uploads/



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            TCG_PCClient_PFP_r1p05_v23_pub.pdf  Section 10.4.1";
       }
       leaf pcr-index {
         type pcr;
         description
           "Defines the PCR index that this event extended";
       }
       list digest-list {
         description
           "Hash of event data";
         leaf hash-algo {
           type identityref {
             base taa:hash;
           }
           description
             "The hash scheme that is used to compress the event data in
              each of the leaf-list digest items.";
         }
         leaf-list digest {
           type binary;
           description
             "The hash of the event data using the algorithm of the
              'hash-algo' against 'event data'.";
         }
       }
       leaf event-size {
         type uint32;
         description
           "Size of the event data";
       }
       leaf-list event-data {
         type binary;
         description
           "The event data.  This is a binary structure
            of size 'event-size'. For more on what
            might be recorded within this object
            see [bios-log] Section 9 which details
            viable events which might be recorded.";
       }
     }

     grouping bios-event-log {
       description
         "Measurement log created by the BIOS/UEFI.";
       list bios-event-entry {
         key "event-number";
         description
           "Ordered list of TCG described event log



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            that extended the PCRs in the order they
            were logged";
         uses boot-event-log;
       }
     }

     grouping ima-event {
       description
         "Defines a hash log extend event for IMA measurements";
       reference
         "ima-log:
          https://www.trustedcomputinggroup.org/wp-content/uploads/
          TCG_IWG_CEL_v1_r0p41_pub.pdf  Section 4.3";
       leaf event-number {
         type uint64;
         description
           "Unique event number of this event which monotonically
            increases.  The maximum event number should not be
            reached, nor is wrapping back to an earlier number
            supported.";
       }
       leaf ima-template {
         type string;
         description
           "Name of the template used for event logs
            for e.g. ima, ima-ng, ima-sig";
       }
       leaf filename-hint {
         type string;
         description
           "File name (including the path) that was measured.";
       }
       leaf filedata-hash {
         type binary;
         description
           "Hash of filedata as updated based upon the
            filedata-hash-algorithm";
       }
       leaf filedata-hash-algorithm {
         type string;
         description
           "Algorithm used for filedata-hash";
       }
       leaf template-hash-algorithm {
         type string;
         description
           "Algorithm used for template-hash";
       }



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       leaf template-hash {
         type binary;
         description
           "hash(filedata-hash, filename-hint)";
       }
       leaf pcr-index {
         type pcr;
         description
           "Defines the PCR index that this event extended";
       }
       leaf signature {
         type binary;
         description
           "Digital file signature which provides a
            fingerprint for the file being measured.";
       }
     }

     grouping ima-event-log {
       description
         "Measurement log created by IMA.";
       list ima-event-entry {
         key "event-number";
         description
           "Ordered list of ima event logs by event-number";
         uses ima-event;
       }
     }

     grouping network-equipment-boot-event-log {
       description
         "Measurement log created by Network Equipment Boot. The Network
          Equipment Boot format is identical to the IMA format. In
          contrast to the IMA log, the Network Equipment Boot log
          includes every measurable event from an Attester, including
          the boot stages of BIOS, Bootloader, etc. In essence, the scope
          of events represented in this format combines the scope of BIOS
          events and IMA events.";
       list boot-event-entry {
         key "event-number";
         description
           "Ordered list of Network Equipment Boot event logs
            by event-number, using the IMA event format.";
         uses ima-event;
       }
     }

     grouping event-logs {



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       description
         "A selector for the log and its type.";
       choice attested_event_log_type {
         mandatory true;
         description
           "Event log type determines the event logs content.";
         case bios {
           if-feature "bios";
           description
             "BIOS/UEFI event logs";
           container bios-event-logs {
             description
               "BIOS/UEFI event logs";
             uses bios-event-log;
           }
         }
         case ima {
           if-feature "ima";
           description
             "IMA event logs.";
           container ima-event-logs {
             description
               "IMA event logs.";
             uses ima-event-log;
           }
         }
         case netequip_boot {
           if-feature "netequip_boot";
           description
             "Network Equipment Boot event logs";
           container boot-event-logs {
             description
               "Network equipment boot event logs.";
             uses network-equipment-boot-event-log;
           }
         }
       }
     }

     /**********************/
     /*   RPC operations   */
     /**********************/

     rpc tpm12-challenge-response-attestation {
       if-feature "taa:tpm12";
       description
         "This RPC accepts the input for TSS TPM 1.2 commands made to the
          attesting device.";



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       input {
         container tpm12-attestation-challenge {
           description
             "This container includes every information element defined
              in the reference challenge-response interaction model for
              remote attestation. Corresponding values are based on
              TPM 1.2 structure definitions";
           uses tpm12-pcr-selection;
           uses nonce;
           leaf-list certificate-name {
             if-feature "tpm:mtpm";
             type certificate-name-ref;
             must "/tpm:rats-support-structures/tpm:tpms"
                + "/tpm:tpm[tpm:firmware-version='taa:tpm12']"
                + "/tpm:certificates/"
                + "/tpm:certificate[name=current()]" {
               error-message "Not an available TPM1.2 AIK certificate.";
             }
             description
               "When populated, the RPC will only get a Quote for the
                TPMs associated with these certificate(s).";
           }
         }
       }
       output {
         list tpm12-attestation-response {
           unique "certificate-name";
           description
             "The binary output of TPM 1.2 TPM_Quote/TPM_Quote2, including
              the PCR selection and other associated attestation evidence
              metadata";
           uses certificate-name-ref {
             description
               "Certificate associated with this tpm12-attestation.";
           }
           uses tpm12-attestation;
         }
       }
     }

     rpc tpm20-challenge-response-attestation {
       if-feature "taa:tpm20";
       description
         "This RPC accepts the input for TSS TPM 2.0 commands of the
          managed device. ComponentIndex from the hardware manager YANG
          module is used to refer to dedicated TPM in composite devices,
          e.g. smart NICs, is not covered.";
       input {



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         container tpm20-attestation-challenge {
           description
             "This container includes every information element defined
              in the reference challenge-response interaction model for
              remote attestation. Corresponding values are based on
              TPM 2.0 structure definitions";
           uses nonce;
           uses tpm20-pcr-selection;
           leaf-list certificate-name {
             if-feature "tpm:mtpm";
             type certificate-name-ref;
             must "/tpm:rats-support-structures/tpm:tpms"
                + "/tpm:tpm[tpm:firmware-version='taa:tpm20']"
                + "/tpm:certificates/"
                + "/tpm:certificate[name=current()]" {
               error-message "Not an available TPM2.0 AIK certificate.";
             }
             description
               "When populated, the RPC will only get a Quote for the
                TPMs associated with the certificates.";
           }
         }
       }
       output {
         list tpm20-attestation-response {
           unique "certificate-name";
           description
             "The binary output of TPM2b_Quote from one TPM of the
              node which identified by node-id. An TPMS_ATTEST structure
              including a length, encapsulated in a signature";
           uses certificate-name-ref {
             description
               "Certificate associated with this tpm20-attestation.";
           }
           uses tpm20-attestation;
         }
       }
     }

     rpc log-retrieval {
       description
         "Logs Entries are either identified via indices or via providing
          the last line received. The number of lines returned can be
          limited. The type of log is a choice that can be augmented.";
       input {
         uses log-identifier;
         list log-selector {
           description



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             "Only log entries which meet all the selection criteria
              provided are to be returned by the RPC output.";
           leaf-list name {
             type string;
             description
               "Name of one or more unique TPMs on a device.  If this
                object exists, a selection should pull only the objects
                related to these TPM(s).  If it does not exist, all
                qualifying TPMs that are 'hardware-based' equals true
                on the device are selected. When this selection
                criteria is provided, it will be considered as a logical
                AND with any other selection criteria provided.";
           }
           choice index-type {
             description
               "Last log entry received, log index number, or timestamp.";
             case last-entry {
               description
                 "The last entry of the log already retrieved.";
               leaf last-entry-value {
                 type binary;
                 description
                   "Content of a log event which matches 1:1 with a
                    unique event record contained within the log.  Log
                    entries after this will be passed to the
                    requester.  Note: if log entry values are not unique,
                    this MUST return an error.";
               }
             }
             case index {
               description
                 "Numeric index of the last log entry retrieved, or
                  zero.";
               leaf last-index-number {
                 type uint64;
                 description
                   "The last numeric index number of a log entry.
                    Zero means to start at the beginning of the log.
                    Entries after this will be passed to the
                    requester.";
               }
             }
             case timestamp {
               leaf timestamp {
                 type yang:date-and-time;
                 description
                   "Timestamp from which to start the extraction.  The
                    next log entry after this timestamp is to



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                    be sent.";
               }
               description
                 "Timestamp from which to start the extraction.";
             }
           }
           leaf log-entry-quantity {
             type uint16;
             description
               "The number of log entries to be returned. If omitted, it
                means all of them.";
           }
         }
       }
       output {
         container system-event-logs {
           description
             "The requested data of the measurement event logs";
           list node-data {
             unique "name";
             description
               "Event logs of a node in a distributed system
                identified by the node name";
             uses tpm-name;
             uses node-uptime;
             container log-result {
               description
                 "The requested entries of the corresponding log.";
               uses event-logs;
             }
           }
         }
       }
     }

     /**************************************/
     /*   Config & Oper accessible nodes   */
     /**************************************/

     container rats-support-structures {
       description
         "The datastore definition enabling verifiers or relying
          parties to discover the information necessary to use the
          remote attestation RPCs appropriately.";
       container compute-nodes {
         if-feature "tpm:mtpm";
         description
           "Holds the set of device subsystems/components in this



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            composite device that support TPM operations.";
         list compute-node {
           key "node-id";
           unique "node-name";
           config false;
           min-elements 2;
           description
             "A component within this composite device which
              supports TPM operations.";
           leaf node-id {
             type string;
             description
               "ID of the compute node, such as Board Serial Number.";
           }
           leaf node-physical-index {
             if-feature "hw:entity-mib";
             type int32 {
               range "1..2147483647";
             }
             config false;
             description
               "The entPhysicalIndex for the compute node.";
             reference
               "RFC 6933: Entity MIB (Version 4) - entPhysicalIndex";
           }
           leaf node-name {
             type string;
             description
               "Name of the compute node.";
           }
           leaf node-location {
             type string;
             description
               "Location of the compute node, such as slot number.";
           }
         }
       }
       container tpms {
         description
           "Holds the set of TPMs within an Attester.";
         list tpm {
           key "name";
           unique "path";
           description
             "A list of TPMs in this composite device that RATS
              can be conducted with.";
           uses tpm-name;
           leaf hardware-based {



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             type boolean;
             config false;
             mandatory true;
             description
               "System generated indication of whether this is a
                hardware based TPM.";
           }
           leaf physical-index {
             if-feature "hw:entity-mib";
             type int32 {
               range "1..2147483647";
             }
             config false;
             description
               "The entPhysicalIndex for the TPM.";
             reference
               "RFC 6933: Entity MIB (Version 4) - entPhysicalIndex";
           }
           leaf path {
             type string;
             config false;
             description
               "Device path to a unique TPM on a device.  This can change
                across reboots.";
           }
           leaf compute-node {
             if-feature "tpm:mtpm";
             type compute-node-ref;
             config false;
             mandatory true;
             description
               "Indicates the compute node measured by this TPM.";
           }
           leaf manufacturer {
             type string;
             config false;
             description
               "TPM manufacturer name.";
           }
           leaf firmware-version {
             type identityref {
               base taa:cryptoprocessor;
             }
             mandatory true;
             description
               "Identifies the cryptoprocessor API set supported.  This
                is automatically configured by the device and should not
                be changed.";



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           }
           uses tpm12-hash-algo {
             when "derived-from-or-self(firmware-version, 'taa:tpm12')";
             if-feature "taa:tpm12";
             refine "tpm12-hash-algo" {
               description
                 "The hash algorithm overwrites the default used for PCRs
                  on this TPM1.2 compliant cryptoprocessor.";
             }
           }
           leaf-list tpm12-pcrs {
             when
               "derived-from-or-self(../firmware-version, 'taa:tpm12')";
             if-feature "taa:tpm12";
             type pcr;
             description
               "The PCRs which may be extracted from this TPM1.2
                compliant cryptoprocessor.";
           }
           list tpm20-pcr-bank {
             when
               "derived-from-or-self(../firmware-version, 'taa:tpm20')";
             if-feature "taa:tpm20";
             key "tpm20-hash-algo";
             description
               "Specifies the list of PCRs that may be extracted for
                a specific Hash Algorithm on this TPM2 compliant
                cryptoprocessor.  A bank is a set of PCRs which are
                extended using a particular hash algorithm.";
             reference
               "TPM2.0-Structures:
                https://www.trustedcomputinggroup.org/wp-content/uploads/
                TPM-Rev-2.0-Part-2-Structures-01.38.pdf  Section 10.9.7";
             leaf tpm20-hash-algo {
               type identityref {
                 base taa:hash;
               }
               must '/tpm:rats-support-structures'
                  + '/tpm:attester-supported-algos'
                  + '/tpm:tpm20-hash' {
                 error-message "This platform does not support tpm20-hash-algo";
               }
               description
                 "The hash scheme actively being used to hash a
                  one or more TPM2.0 PCRs.";
             }
             leaf-list pcr-index {
               type tpm:pcr;



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               description
                 "Defines what TPM2 PCRs are available to be extracted.";
             }
           }
           leaf status {
             type enumeration {
               enum operational {
                 value 0;
                 description
                   "The TPM currently is running normally and
                    is ready to accept and process TPM quotes.";
                 reference
                   "TPM2.0-Arch:
                    https://trustedcomputinggroup.org/wp-content/uploads/
                    TCG_TPM2_r1p59_Part1_Architecture_pub.pdf
                    Section 12";
               }
               enum non-operational {
                 value 1;
                 description
                   "TPM is in a state such as startup or shutdown which
                    precludes the processing of TPM quotes.";
               }
             }
             config false;
             mandatory true;
             description
               "TPM chip self-test status.";
           }
           container certificates {
             description
               "The TPM's certificates, including EK certificates
                and Attestation Key certificates.";
             list certificate {
               key "name";
               description
                 "Three types of certificates can be accessed via
                  this statement, including Initial Attestation
                  Key Certificate, Local Attestation Key Certificate or
                  Endorsement Key Certificate.";
               leaf name {
                 type string;
                 description
                   "An arbitrary name uniquely identifying a certificate
                    associated within key within a TPM.";
               }
               leaf keystore-ref {
                 if-feature "ks:asymmetric-keys";



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                 type leafref {
                   path "/ks:keystore/ks:asymmetric-keys/ks:asymmetric-key"
                      + "/ks:name";
                 }
                 description
                   "A reference to a specific certificate of an
                    asymmetric key in the Keystore.";
               }
               leaf type {
                 type enumeration {
                   enum endorsement-certificate {
                     value 0;
                     description
                       "Endorsement Key (EK) Certificate type.";
                     reference
                       "TPM2.0-Key:
                        https://trustedcomputinggroup.org/wp-content/
                        uploads/TPM-2p0-Keys-for-Device-Identity-
                        and-Attestation_v1_r12_pub10082021.pdf
                        Section 3.11";
                   }
                   enum initial-attestation-certificate {
                     value 1;
                     description
                       "Initial Attestation key (IAK) Certificate type.";
                     reference
                       "TPM2.0-Key:
                        https://trustedcomputinggroup.org/wp-content/
                        uploads/TPM-2p0-Keys-for-Device-Identity-
                        and-Attestation_v1_r12_pub10082021.pdf
                        Section 3.2";
                   }
                   enum local-attestation-certificate {
                     value 2;
                     description
                       "Local Attestation Key (LAK) Certificate type.";
                     reference
                       "TPM2.0-Key:
                        https://trustedcomputinggroup.org/wp-content/
                        uploads/TPM-2p0-Keys-for-Device-Identity-
                        and-Attestation_v1_r12_pub10082021.pdf
                        Section 3.2";
                   }
                 }
                 description
                   "Function supported by this certificate from within the
                    TPM.";
               }



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             }
           }
         }
       }
       container attester-supported-algos {
         description
           "Identifies which TPM algorithms are available for use on an
            attesting platform.";
         leaf-list tpm12-asymmetric-signing {
           when "../../tpm:tpms"
              + "/tpm:tpm[tpm:firmware-version='taa:tpm12']";
           if-feature "taa:tpm12";
           type identityref {
             base taa:asymmetric;
           }
           description
             "Platform Supported TPM12 asymmetric algorithms.";
         }
         leaf-list tpm12-hash {
           when "../../tpm:tpms"
              + "/tpm:tpm[tpm:firmware-version='taa:tpm12']";
           if-feature "taa:tpm12";
           type identityref {
             base taa:hash;
           }
           description
             "Platform supported TPM12 hash algorithms.";
         }
         leaf-list tpm20-asymmetric-signing {
           when "../../tpm:tpms"
              + "/tpm:tpm[tpm:firmware-version='taa:tpm20']";
           if-feature "taa:tpm20";
           type identityref {
             base taa:asymmetric;
           }
           description
             "Platform Supported TPM20 asymmetric algorithms.";
         }
         leaf-list tpm20-hash {
           when "../../tpm:tpms"
              + "/tpm:tpm[tpm:firmware-version='taa:tpm20']";
           if-feature "taa:tpm20";
           type identityref {
             base taa:hash;
           }
           description
             "Platform supported TPM20 hash algorithms.";
         }



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       }
     }
   }
   <CODE ENDS>

                                  Figure 1

2.1.2.  'ietf-tcg-algs'

   This document has encoded the TCG Algorithm definitions of
   [TCG-Algos], revision 1.32.  By including this full table as a
   separate YANG file within this document, it is possible for other
   YANG models to leverage the contents of this model.  Specific
   references to [RFC2104], [RFC8017], [ISO-IEC-9797-1],
   [ISO-IEC-9797-2], [ISO-IEC-10116], [ISO-IEC-10118-3],
   [ISO-IEC-14888-3], [ISO-IEC-15946-1], [ISO-IEC-18033-3],
   [IEEE-Std-1363-2000], [IEEE-Std-1363a-2004], [NIST-PUB-FIPS-202],
   [NIST-SP800-38C], [NIST-SP800-38D], [NIST-SP800-38F],
   [NIST-SP800-56A], [NIST-SP800-108], [bios-log], as well as Appendix A
   and Appendix B exist within the YANG Model.

2.1.2.1.  Features

   There are two types of features supported: 'TPM12' and 'TPM20'.
   Support for either of these features indicates that a cryptoprocessor
   supporting the corresponding type of TCG TPM API is present on an
   Attester.  Most commonly, only one type of cryptoprocessor will be
   available on an Attester.

2.1.2.2.  Identities

   There are three types of identities in this model:

   1.  Cryptographic functions supported by a TPM algorithm; these
       include: 'asymmetric', 'symmetric', 'hash', 'signing',
       'anonymous_signing', 'encryption_mode', 'method', and
       'object_type'.  The definitions of each of these are in Table 2
       of [TCG-Algos].

   2.  API specifications for TPM types: 'tpm12' and 'tpm20'

   3.  Specific algorithm types: Each algorithm type defines what
       cryptographic functions may be supported, and on which type of
       API specification.  It is not required that an implementation of
       a specific TPM will support all algorithm types.  The contents of
       each specific algorithm mirrors what is in Table 3 of
       [TCG-Algos].




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2.1.2.3.  YANG Module

   <CODE BEGINS> file "ietf-tcg-algs@2022-03-23.yang"
   module ietf-tcg-algs {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-tcg-algs";
     prefix taa;

     organization
       "IETF RATS (Remote ATtestation procedureS) Working Group";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/rats/>
        WG List:  <mailto:rats@ietf.org>
        Author:   Eric Voit <mailto:evoit@cisco.com>";
     description
       "This module defines identities for asymmetric algorithms.

        Copyright (c) 2022 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 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 2022-03-23 {
       description
         "Initial version";
       reference
         "RFC XXXX: A YANG Data Model for Challenge-Response-based Remote
          Attestation Procedures using TPMs";
     }

     /*****************/
     /*   Features    */
     /*****************/



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     feature tpm12 {
       description
         "This feature indicates algorithm support for the TPM 1.2 API
          as per Section 4.8 of TPM1.2-Structures:
          TPM Main Part 2 TPM Structures
          https://trustedcomputinggroup.org/wp-content/uploads/TPM-
          Main-Part-2-TPM-Structures_v1.2_rev116_01032011.pdf";
     }

     feature tpm20 {
       description
         "This feature indicates algorithm support for the TPM 2.0 API
          as per Section 11.4 of Trusted Platform Module Library
          Part 1: Architecture. See TPM2.0-Arch:
          https://trustedcomputinggroup.org/wp-content/uploads/
          TCG_TPM2_r1p59_Part1_Architecture_pub.pdf";
     }

     /*****************/
     /*  Identities   */
     /*****************/

     identity asymmetric {
       description
         "A TCG recognized asymmetric algorithm with a public and
          private key.";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 2,
          https://trustedcomputinggroup.org/resource/
          tcg-algorithm-registry/TCG-_Algorithm_Registry_r1p32_pub";
     }

     identity symmetric {
       description
         "A TCG recognized symmetric algorithm with only a private key.";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 2";
     }

     identity hash {
       description
         "A TCG recognized hash algorithm that compresses input data to
          a digest value or indicates a method that uses a hash.";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 2";
     }

     identity signing {



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       description
         "A TCG recognized signing algorithm";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 2";
     }

     identity anonymous_signing {
       description
         "A TCG recognized anonymous signing algorithm.";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 2";
     }

     identity encryption_mode {
       description
         "A TCG recognized encryption mode.";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 2";
     }

     identity method {
       description
         "A TCG recognized method such as a mask generation function.";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 2";
     }

     identity object_type {
       description
         "A TCG recognized object type.";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 2";
     }

     identity cryptoprocessor {
       description
         "Base identity identifying a crytoprocessor.";
     }

     identity tpm12 {
       if-feature "tpm12";
       base cryptoprocessor;
       description
         "Supportable by a TPM1.2.";
       reference
         "TPM1.2-Structures:
          https://trustedcomputinggroup.org/wp-content/uploads/
          TPM-Main-Part-2-TPM-Structures_v1.2_rev116_01032011.pdf



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          TPM_ALGORITHM_ID values, Section 4.8";
     }

     identity tpm20 {
       if-feature "tpm20";
       base cryptoprocessor;
       description
         "Supportable by a TPM2.";
       reference
         "TPM2.0-Structures:
          https://trustedcomputinggroup.org/wp-content/uploads/
          TPM-Rev-2.0-Part-2-Structures-01.38.pdf";
     }

     identity TPM_ALG_RSA {
       if-feature "tpm12 or tpm20";
       base tpm12;
       base tpm20;
       base asymmetric;
       base object_type;
       description
         "RSA algorithm";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          RFC 8017. ALG_ID: 0x0001";
     }

     identity TPM_ALG_TDES {
       if-feature "tpm12";
       base tpm12;
       base symmetric;
       description
         "Block cipher with various key sizes (Triple Data Encryption
          Algorithm, commonly called Triple Data Encryption Standard)
          Note: was banned in TPM1.2 v94";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 18033-3. ALG_ID: 0x0003";
     }

     identity TPM_ALG_SHA1 {
       if-feature "tpm12 or tpm20";
       base hash;
       base tpm12;
       base tpm20;
       description
         "SHA1 algorithm - Deprecated due to insufficient cryptographic
          protection.  However, it is still useful for hash algorithms



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          where protection is not required.";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 10118-3. ALG_ID: 0x0004";
     }

     identity TPM_ALG_HMAC {
       if-feature "tpm12 or tpm20";
       base tpm12;
       base tpm20;
       base hash;
       base signing;
       description
         "Hash Message Authentication Code (HMAC) algorithm";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3,
          ISO/IEC 9797-2 and RFC2104. ALG_ID: 0x0005";
     }

     identity TPM_ALG_AES {
       if-feature "tpm12";
       base tpm12;
       base symmetric;
       description
         "The AES algorithm with various key sizes";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3,
          ISO/IEC 18033-3. ALG_ID: 0x0006";
     }

     identity TPM_ALG_MGF1 {
       if-feature "tpm20";
       base tpm20;
       base hash;
       base method;
       description
         "hash-based mask-generation function";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3,
          IEEE Std 1363-2000 and IEEE Std 1363a-2004.
          ALG_ID: 0x0007";
     }

     identity TPM_ALG_KEYEDHASH {
       if-feature "tpm20";
       base tpm20;
       base hash;
       base object_type;



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       description
         "An encryption or signing algorithm using a keyed hash.  These
          may use XOR for encryption or an HMAC for signing and may
          also refer to a data object that is neither signing nor
          encrypting.";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3,
          ALG_ID: 0x0008";
     }

     identity TPM_ALG_XOR {
       if-feature "tpm12 or tpm20";
       base tpm12;
       base tpm20;
       base hash;
       base symmetric;
       description
         "The XOR encryption algorithm.";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3.
          ALG_ID: 0x000A";
     }

     identity TPM_ALG_SHA256 {
       if-feature "tpm20";
       base tpm20;
       base hash;
       description
         "The SHA 256 algorithm";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 10118-3. ALG_ID: 0x000B";
     }

     identity TPM_ALG_SHA384 {
       if-feature "tpm20";
       base tpm20;
       base hash;
       description
         "The SHA 384 algorithm";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 10118-3. ALG_ID: 0x000C";
     }

     identity TPM_ALG_SHA512 {
       if-feature "tpm20";
       base tpm20;



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       base hash;
       description
         "The SHA 512 algorithm";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 10118-3. ALG_ID: 0x000D";
     }

     identity TPM_ALG_NULL {
       if-feature "tpm20";
       base tpm20;
       description
         "NULL algorithm";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3.
          ALG_ID: 0x0010";
     }

     identity TPM_ALG_SM3_256 {
       if-feature "tpm20";
       base tpm20;
       base hash;
       description
         "The SM3 hash algorithm.";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 10118-3:2018. ALG_ID: 0x0012";
     }

     identity TPM_ALG_SM4 {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       description
         "SM4 symmetric block cipher";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3.
          ALG_ID: 0x0013";
     }

     identity TPM_ALG_RSASSA {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       description
         "RFC 8017 Signature algorithm defined in section 8.2
          (RSASSAPKCS1-v1_5)";



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       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          RFC 8017.  ALG_ID: 0x0014";
     }

     identity TPM_ALG_RSAES {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base encryption_mode;
       description
         "RFC 8017 Signature algorithm defined in section 7.2
          (RSAES-PKCS1-v1_5)";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          RFC 8017. ALG_ID: 0x0015";
     }

     identity TPM_ALG_RSAPSS {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       description
         "Padding algorithm defined in section 8.1 (RSASSA PSS)";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          RFC 8017. ALG_ID: 0x0016";
     }

     identity TPM_ALG_OAEP {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base encryption_mode;
       description
         "Padding algorithm defined in section 7.1 (RSASSA OAEP)";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          RFC 8017. ALG_ID: 0x0017";
     }

     identity TPM_ALG_ECDSA {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       description



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         "Signature algorithm using elliptic curve cryptography (ECC)";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 14888-3. ALG_ID: 0x0018";
     }

     identity TPM_ALG_ECDH {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base method;
       description
         "Secret sharing using ECC";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          NIST SP800-56A. ALG_ID: 0x0019";
     }

     identity TPM_ALG_ECDAA {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       base anonymous_signing;
       description
         "Elliptic-curve based anonymous signing scheme";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          TCG TPM 2.0 library specification. ALG_ID: 0x001A";
     }

     identity TPM_ALG_SM2 {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       base encryption_mode;
       base method;
       description
         "SM2 - depending on context, either an elliptic-curve based,
          signature algorithm, an encryption scheme, or a key exchange
          protocol";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3.
          ALG_ID: 0x001B";
     }

     identity TPM_ALG_ECSCHNORR {



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       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       description
         "Elliptic-curve based Schnorr signature";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3.
          ALG_ID: 0x001C";
     }

     identity TPM_ALG_ECMQV {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base method;
       description
         "Two-phase elliptic-curve key";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          NIST SP800-56A. ALG_ID: 0x001D";
     }

     identity TPM_ALG_KDF1_SP800_56A {
       if-feature "tpm20";
       base tpm20;
       base hash;
       base method;
       description
         "Concatenation key derivation function";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          NIST SP800-56A  (approved alternative1) section 5.8.1.
          ALG_ID: 0x0020";
     }

     identity TPM_ALG_KDF2 {
       if-feature "tpm20";
       base tpm20;
       base hash;
       base method;
       description
         "Key derivation function";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          IEEE 1363a-2004 KDF2 section 13.2. ALG_ID: 0x0021";
     }




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     identity TPM_ALG_KDF1_SP800_108 {
       base TPM_ALG_KDF2;
       description
         "A key derivation method";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          NIST SP800-108 - Section 5.1 KDF. ALG_ID: 0x0022";
     }

     identity TPM_ALG_ECC {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base object_type;
       description
         "Prime field ECC";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 15946-1. ALG_ID: 0x0023";
     }

     identity TPM_ALG_SYMCIPHER {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base object_type;
       description
         "Object type for a symmetric block cipher";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          TCG TPM 2.0 library specification. ALG_ID: 0x0025";
     }

     identity TPM_ALG_CAMELLIA {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       description
         "The Camellia algorithm";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 18033-3. ALG_ID: 0x0026";
     }

     identity TPM_ALG_SHA3_256 {
       if-feature "tpm20";
       base tpm20;
       base hash;



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       description
         "ISO/IEC 10118-3 - the SHA 256 algorithm";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          NIST PUB FIPS 202. ALG_ID: 0x0027";
     }

     identity TPM_ALG_SHA3_384 {
       if-feature "tpm20";
       base tpm20;
       base hash;
       description
         "The SHA 384 algorithm";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          NIST PUB FIPS 202. ALG_ID: 0x0028";
     }

     identity TPM_ALG_SHA3_512 {
       if-feature "tpm20";
       base tpm20;
       base hash;
       description
         "The SHA 512 algorithm";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          NIST PUB FIPS 202. ALG_ID: 0x0029";
     }

     identity TPM_ALG_CMAC {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base signing;
       description
         "block Cipher-based Message Authentication Code (CMAC)";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 9797-1:2011 Algorithm 5. ALG_ID: 0x003F";
     }

     identity TPM_ALG_CTR {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base encryption_mode;
       description
         "Counter mode";



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       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 10116. ALG_ID: 0x0040";
     }

     identity TPM_ALG_OFB {
       base tpm20;
       base symmetric;
       base encryption_mode;
       description
         "Output Feedback mode";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 10116. ALG_ID: 0x0041";
     }

     identity TPM_ALG_CBC {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base encryption_mode;
       description
         "Cipher Block Chaining mode";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 10116. ALG_ID: 0x0042";
     }

     identity TPM_ALG_CFB {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base encryption_mode;
       description
         "Cipher Feedback mode";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 10116. ALG_ID: 0x0043";
     }

     identity TPM_ALG_ECB {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base encryption_mode;
       description
         "Electronic Codebook mode";
       reference



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         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          ISO/IEC 10116. ALG_ID: 0x0044";
     }

     identity TPM_ALG_CCM {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base signing;
       base encryption_mode;
       description
         "Counter with Cipher Block Chaining-Message Authentication
          Code (CCM)";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          NIST SP800-38C. ALG_ID: 0x0050";
     }

     identity TPM_ALG_GCM {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base signing;
       base encryption_mode;
       description
         "Galois/Counter Mode (GCM)";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          NIST SP800-38D. ALG_ID: 0x0051";
     }

     identity TPM_ALG_KW {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base signing;
       base encryption_mode;
       description
         "AES Key Wrap (KW)";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          NIST SP800-38F. ALG_ID: 0x0052";
     }

     identity TPM_ALG_KWP {
       if-feature "tpm20";
       base tpm20;
       base symmetric;



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       base signing;
       base encryption_mode;
       description
         "AES Key Wrap with Padding (KWP)";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          NIST SP800-38F. ALG_ID: 0x0053";
     }

     identity TPM_ALG_EAX {
       if-feature "tpm20";
       base tpm20;
       base symmetric;
       base signing;
       base encryption_mode;
       description
         "Authenticated-Encryption Mode";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          NIST SP800-38F. ALG_ID: 0x0054";
     }

     identity TPM_ALG_EDDSA {
       if-feature "tpm20";
       base tpm20;
       base asymmetric;
       base signing;
       description
         "Edwards-curve Digital Signature Algorithm (PureEdDSA)";
       reference
         "TCG-Algos:TCG Algorithm Registry Rev1.32  Table 3 and
          RFC 8032. ALG_ID: 0x0060";
     }
   }
   <CODE ENDS>

   Note that not all cryptographic functions are required for use by
   ietf-tpm-remote-attestation.yang.  However the full definition of
   Table 3 of [TCG-Algos] will allow use by additional YANG
   specifications.

3.  IANA Considerations

   This document registers the following namespace URIs in the
   [xml-registry] as per [RFC3688]:

   URI:  urn:ietf:params:xml:ns:yang:ietf-tpm-remote-attestation




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      Registrant Contact:  The IESG.

      XML:  N/A; the requested URI is an XML namespace.

   URI:  urn:ietf:params:xml:ns:yang:ietf-tcg-algs

      Registrant Contact:  The IESG.

      XML:  N/A; the requested URI is an XML namespace.

   This document registers the following YANG modules in the registry
   [yang-parameters] as per Section 14 of [RFC6020]:

   Name:  ietf-tpm-remote-attestation

      Namespace:  urn:ietf:params:xml:ns:yang:ietf-tpm-remote-
         attestation

      Prefix:  tpm

      Reference:  draft-ietf-rats-yang-tpm-charra (RFC form)

   Name:  ietf-tcg-algs

      Namespace:  urn:ietf:params:xml:ns:yang:ietf-tcg-algs

      Prefix:  taa

      Reference:  draft-ietf-rats-yang-tpm-charra (RFC form)

4.  Security Considerations

   The YANG module ietf-tpm-remote-attestation.yang specified in this
   document defines a schema for data that is designed to be accessed
   via network management protocols such as NETCONF [RFC6241] or
   RESTCONF [RFC8040].  The lowest NETCONF layer is the secure transport
   layer, and the mandatory-to-implement secure transport is Secure
   Shell (SSH) [RFC6242].  The lowest RESTCONF layer is HTTPS, and the
   mandatory-to-implement secure transport is TLS [RFC8446].

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., _config true_, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., _edit-config_)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   as well as their sensitivity/vulnerability:




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   Container '/rats-support-structures/attester-supported-algos':  'tpm1
      2-asymmetric-signing', 'tpm12-hash', 'tpm20-asymmetric-signing',
      and 'tpm20-hash'.  All could be populated with algorithms that are
      not supported by the underlying physical TPM installed by the
      equipment vendor.  A vendor should restrict the ability to
      configure unsupported algorithms.

   Container: '/rats-support-structures/tpms':  'name': Although shown
      as 'rw', it is system generated.  Therefore, it should not be
      possible for an operator to add or remove a TPM from the
      configuration.

      'tpm20-pcr-bank': It is possible to configure PCRs for extraction
      which are not being extended by system software.  This could
      unnecessarily use TPM resources.

      'certificates': It is possible to provision a certificate which
      does not correspond to an Attestation Identity Key (AIK) within
      the TPM 1.2, or an Attestation Key (AK) within the TPM 2.0
      respectively.  In such a case, calls to an RPC requesting this
      specific certificate could result in either no response or a
      response for an unexpected TPM.

   RPC 'tpm12-challenge-response-attestation':  The receiver of the RPC
      response must verify that the certificate is for an active AIK,
      i.e., the certificate has been confirmed by a third party as being
      able to support Attestation on the targeted TPM 1.2.

   RPC 'tpm20-challenge-response-attestation':  The receiver of the RPC
      response must verify that the certificate is for an active AK,
      i.e., the private key confirmation of the quote signature within
      the RPC response has been confirmed by a third party to belong to
      an entity legitimately able to perform Attestation on the targeted
      TPM 2.0.

   RPC 'log-retrieval':  Requesting a large volume of logs from the
      attester could require significant system resources and create a
      denial of service.

   Information collected through the RPCs above could reveal that
   specific versions of software and configurations of endpoints that
   could identify vulnerabilities on those systems.  Therefore, RPCs
   should be protected by NACM [RFC8341] with a default setting of deny-
   all to limit the extraction of attestation data by only authorized
   Verifiers.






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   For the YANG module ietf-tcg-algs.yang, please use care when
   selecting specific algorithms.  The introductory section of
   [TCG-Algos] highlights that some algorithms should be considered
   legacy, and recommends implementers and adopters diligently evaluate
   available information such as governmental, industrial, and academic
   research before selecting an algorithm for use.

5.  References

5.1.  Normative References

   [bios-log] "TCG PC Client Platform Firmware Profile Specification,
              Section 9.4.5.2", n.d.,
              <https://trustedcomputinggroup.org/wp-content/uploads/PC-C
              lientSpecific_Platform_Profile_for_TPM_2p0_Systems_v51.pdf
              >.

   [BIOS-Log-Event-Type]
              "TCG PC Client Platform Firmware Profile Specification",
              n.d., <https://trustedcomputinggroup.org/wp-
              content/uploads/TCG_PCClient_PFP_r1p05_v23_pub.pdf>.

   [cel]      "Canonical Event Log Format, Section 4.3", n.d.,
              <https://trustedcomputinggroup.org/wp-content/uploads/
              TCG_IWG_CEL_v1_r0p41_pub.pdf>.

   [I-D.ietf-netconf-keystore]
              Watsen, K., "A YANG Data Model for a Keystore", Work in
              Progress, Internet-Draft, draft-ietf-netconf-keystore-24,
              7 March 2022, <https://www.ietf.org/archive/id/draft-ietf-
              netconf-keystore-24.txt>.

   [I-D.ietf-rats-architecture]
              Birkholz, H., Thaler, D., Richardson, M., Smith, N., and
              W. Pan, "Remote Attestation Procedures Architecture", Work
              in Progress, Internet-Draft, draft-ietf-rats-architecture-
              15, 8 February 2022, <https://www.ietf.org/archive/id/
              draft-ietf-rats-architecture-15.txt>.

   [I-D.ietf-rats-tpm-based-network-device-attest]
              Fedorkow, G., Voit, E., and J. Fitzgerald-McKay, "TPM-
              based Network Device Remote Integrity Verification", Work
              in Progress, Internet-Draft, draft-ietf-rats-tpm-based-
              network-device-attest-14, 22 March 2022,
              <https://www.ietf.org/archive/id/draft-ietf-rats-tpm-
              based-network-device-attest-14.txt>.





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   [IEEE-Std-1363-2000]
              "IEEE 1363-2000 - IEEE Standard Specifications for Public-
              Key Cryptography", n.d.,
              <https://standards.ieee.org/standard/1363-2000.html>.

   [IEEE-Std-1363a-2004]
              "1363a-2004 - IEEE Standard Specifications for Public-Key
              Cryptography - Amendment 1: Additional Techniques", n.d.,
              <https://ieeexplore.ieee.org/document/1335427>.

   [ISO-IEC-10116]
              "ISO/IEC 10116:2017 - Information technology", n.d.,
              <https://www.iso.org/standard/64575.html>.

   [ISO-IEC-10118-3]
              "Dedicated hash-functions - ISO/IEC 10118-3:2018", n.d.,
              <https://www.iso.org/standard/67116.html>.

   [ISO-IEC-14888-3]
              "ISO/IEC 14888-3:2018 - Digital signatures with appendix",
              n.d., <https://www.iso.org/standard/76382.html>.

   [ISO-IEC-15946-1]
              "ISO/IEC 15946-1:2016 - Information technology", n.d.,
              <https://www.iso.org/standard/65480.html>.

   [ISO-IEC-18033-3]
              "ISO/IEC 18033-3:2010 - Encryption algorithms", n.d.,
              <https://www.iso.org/standard/54531.html>.

   [ISO-IEC-9797-1]
              "Message Authentication Codes (MACs) - ISO/IEC
              9797-1:2011", n.d.,
              <https://www.iso.org/standard/50375.html>.

   [ISO-IEC-9797-2]
              "Message Authentication Codes (MACs) - ISO/IEC
              9797-2:2011", n.d.,
              <https://www.iso.org/standard/51618.html>.

   [NIST-PUB-FIPS-202]
              "SHA-3 Standard: Permutation-Based Hash and Extendable-
              Output Functions", n.d.,
              <https://csrc.nist.gov/publications/detail/fips/202/
              final>.






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   [NIST-SP800-108]
              "Recommendation for Key Derivation Using Pseudorandom
              Functions", n.d.,
              <https://nvlpubs.nist.gov/nistpubs/Legacy/SP/
              nistspecialpublication800-108.pdf>.

   [NIST-SP800-38C]
              "Recommendation for Block Cipher Modes of Operation: the
              CCM Mode for Authentication and Confidentiality", n.d.,
              <https://csrc.nist.gov/publications/detail/sp/800-38c/
              final>.

   [NIST-SP800-38D]
              "Recommendation for Block Cipher Modes of Operation:
              Galois/Counter Mode (GCM) and GMAC", n.d.,
              <https://csrc.nist.gov/publications/detail/sp/800-38d/
              final>.

   [NIST-SP800-38F]
              "Recommendation for Block Cipher Modes of Operation:
              Methods for Key Wrapping", n.d.,
              <https://csrc.nist.gov/publications/detail/sp/800-38f/
              final>.

   [NIST-SP800-56A]
              "Recommendation for Pair-Wise Key-Establishment Schemes
              Using Discrete Logarithm Cryptography", n.d.,
              <https://csrc.nist.gov/publications/detail/sp/800-56a/rev-
              3/final>.

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104,
              DOI 10.17487/RFC2104, February 1997,
              <https://www.rfc-editor.org/info/rfc2104>.

   [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>.



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   [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>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC6933]  Bierman, A., Romascanu, D., Quittek, J., and M.
              Chandramouli, "Entity MIB (Version 4)", RFC 6933,
              DOI 10.17487/RFC6933, May 2013,
              <https://www.rfc-editor.org/info/rfc6933>.

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

   [RFC8017]  Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch,
              "PKCS #1: RSA Cryptography Specifications Version 2.2",
              RFC 8017, DOI 10.17487/RFC8017, November 2016,
              <https://www.rfc-editor.org/info/rfc8017>.

   [RFC8032]  Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
              Signature Algorithm (EdDSA)", RFC 8032,
              DOI 10.17487/RFC8032, January 2017,
              <https://www.rfc-editor.org/info/rfc8032>.

   [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>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8348]  Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A
              YANG Data Model for Hardware Management", RFC 8348,
              DOI 10.17487/RFC8348, March 2018,
              <https://www.rfc-editor.org/info/rfc8348>.






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   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [TCG-Algos]
              "TCG Algorithm Registry", n.d.,
              <https://trustedcomputinggroup.org/wp-content/uploads/TCG-
              _Algorithm_Registry_r1p32_pub.pdf>.

   [TPM1.2]   TCG, "TPM 1.2 Main Specification", 2 October 2003,
              <https://trustedcomputinggroup.org/resource/tpm-main-
              specification/>.

   [TPM1.2-Commands]
              "TPM Main Part 3 Commands", n.d.,
              <https://trustedcomputinggroup.org/wp-content/uploads/TPM-
              Main-Part-3-Commands_v1.2_rev116_01032011.pdf>.

   [TPM1.2-Structures]
              "TPM Main Part 2 TPM Structures", n.d.,
              <https://trustedcomputinggroup.org/wp-content/uploads/TPM-
              Main-Part-2-TPM-Structures_v1.2_rev116_01032011.pdf>.

   [TPM2.0]   TCG, "TPM 2.0 Library Specification", 15 March 2013,
              <https://trustedcomputinggroup.org/resource/tpm-library-
              specification/>.

   [TPM2.0-Arch]
              "Trusted Platform Module Library - Part 1: Architecture",
              n.d., <https://trustedcomputinggroup.org/wp-
              content/uploads/
              TCG_TPM2_r1p59_Part1_Architecture_pub.pdf>.

   [TPM2.0-Key]
              TCG, "TPM 2.0 Keys for Device Identity and Attestation,
              Rev12", 8 October 2021,
              <https://trustedcomputinggroup.org/wp-content/uploads/TPM-
              2p0-Keys-for-Device-Identity-and-
              Attestation_v1_r12_pub10082021.pdf>.

   [TPM2.0-Structures]
              "Trusted Platform Module Library - Part 2: Structures",
              n.d., <https://trustedcomputinggroup.org/wp-
              content/uploads/TPM-Rev-2.0-Part-2-Structures-01.38.pdf>.

   [UEFI-Secure-Boot]
              "Unified Extensible Firmware Interface (UEFI)
              Specification Version 2.9 (March 2021), Section 32.1



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              (Secure Boot)", n.d.,
              <https://uefi.org/sites/default/files/resources/
              UEFI_Spec_2_9_2021_03_18.pdf>.

5.2.  Informative References

   [I-D.ietf-rats-reference-interaction-models]
              Birkholz, H., Eckel, M., Pan, W., and E. Voit, "Reference
              Interaction Models for Remote Attestation Procedures",
              Work in Progress, Internet-Draft, draft-ietf-rats-
              reference-interaction-models-05, 26 January 2022,
              <https://www.ietf.org/archive/id/draft-ietf-rats-
              reference-interaction-models-05.txt>.

   [IMA-Kernel-Source]
              "Linux Integrity Measurement Architecture (IMA): Kernel
              Sourcecode", n.d., <https://github.com/torvalds/linux/blob
              /df0cc57e057f18e44dac8e6c18aba47ab53202f9/security/
              integrity/ima/>.

   [NIST-915121]
              "True Randomness Can't be Left to Chance: Why entropy is
              important for information security", n.d.,
              <https://tsapps.nist.gov/publication/
              get_pdf.cfm?pub_id=915121>.

   [xml-registry]
              "IETF XML Registry", n.d.,
              <https://www.iana.org/assignments/xml-registry/xml-
              registry.xhtml>.

   [yang-parameters]
              "YANG Parameters", n.d.,
              <https://www.iana.org/assignments/yang-parameters/yang-
              parameters.xhtml>.

Appendix A.  Integrity Measurement Architecture (IMA)

   IMA extends the principles of Measured Boot [TPM2.0-Arch] and Secure
   Boot [UEFI-Secure-Boot] to the Linux operating system, applying it to
   operating system applications and files.  IMA has been part of the
   Linux integrity subsystem of the Linux kernel since 2009 (kernel
   version 2.6.30).  The IMA mechanism represented by the YANG module in
   this specification is rooted in the kernel version 5.16
   [IMA-Kernel-Source].  IMA enables the protection of system integrity
   by collecting (commonly referred to as measuring) and storing
   measurements (called Claims in the context of IETF RATS) of files
   before execution so that these measurements can be used later, at



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   system runtime, in remote attestation procedures.  IMA acts in
   support of the appraisal of Evidence (which includes measurement
   Claims) by leveraging reference integrity measurements stored in
   extended file attributes.

   In support of the appraisal of Evidence, IMA maintains an ordered
   list of measurements in kernel-space, the Stored Measurement Log
   (SML), for all files that have been measured before execution since
   the operating system was started.  Although IMA can be used without a
   TPM, it is typically used in conjunction with a TPM to anchor the
   integrity of the SML in a hardware-protected secure storage location,
   i.e., Platform Configuration Registers (PCRs) provided by TPMs.  IMA
   provides the SML in both binary and ASCII representations in the
   Linux security file system _securityfs_ (/sys/kernel/security/ima/).

   IMA templates define the format of the SML, i.e., which fields are
   included in a log record.  Examples are file path, file hash, user
   ID, group ID, file signature, and extended file attributes.  IMA
   comes with a set of predefined template formats and also allows a
   custom format, i.e., a format consisting of template fields supported
   by IMA.  Template usage is typically determined by boot arguments
   passed to the kernel.  Alternatively, the format can also be hard-
   coded into custom kernels.  IMA templates and fields are extensible
   in the kernel source code.  As a result, more template fields can be
   added in the future.

   IMA policies define which files are measured using the IMA policy
   language.  Built-in policies can be passed as boot arguments to the
   kernel.  Custom IMA policies can be defined once during runtime or be
   hard-coded into a custom kernel.  If no policy is defined, no
   measurements are taken and IMA is effectively disabled.

   A comprehensive description of the content fields ins in native Linux
   IMA TLV format can be found in Table 16 of the Canonical Event Log
   (CEL) specification [cel].  The CEL specification also illustrates
   the use of templates to enable extended or customized IMA TLV formats
   in Section 5.1.6.

Appendix B.  IMA for Network Equipment Boot Logs

   Network equipment can generally implement similar IMA-protected
   functions to generate measurements (Claims) about the boot process of
   a device and enable corresponding remote attestation.  Network
   Equipment Boot Logs combine the measurement and logging of boot
   components and operating system components (executables and files)
   into a single log file in a format identical to the IMA format.  Note
   that the format used for logging measurement of boot components in
   this scheme differs from the boot logging strategy described



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   elsewhere in this document.

   During the boot process of the network device, i.e., from BIOS to the
   end of the operating system and user-space, all files executed can be
   measured and logged in the order of their execution.  When the
   Verifier initiates a remote attestation process (e.g., challenge-
   response remote attestation as defined in this document), the network
   equipment takes on the role of an Attester and can convey to the
   Verifier Claims that comprise the measurement log as well as the
   corresponding PCR values (Evidence) of a TPM.

   The verifier can appraise the integrity (compliance with the
   Reference Values) of each executed file by comparing its measured
   value with the Reference Value.  Based on the execution order, the
   Verifier can compute a PCR reference value (by replaying the log) and
   compare it to the Measurement Log Claims obtained in conjunction with
   the PCR Evidence to assess their trustworthiness with respect to an
   intended operational state.

   Network equipment usually executes multiple components in parallel.
   This holds not only during the operating system loading phase, but
   also even during the BIOS boot phase.  With this measurement log
   mechanism, network equipment can take on the role of an Attester,
   proving to the Verifier the trustworthiness of its boot process.
   Using the measurement log, Verifiers can precisely identify
   mismatching log entries to infer potentially tampered components.

   This mechanism also supports scenarios that modify files on the
   Attester that are subsequently executed during the boot phase (e.g.,
   updating/patching) by simply updating the appropriate Reference
   Values in Reference Integrity Manifests that inform Verifiers about
   how an Attester is composed.

Authors' Addresses

   Henk Birkholz
   Fraunhofer SIT
   Rheinstrasse 75
   64295 Darmstadt
   Germany
   Email: henk.birkholz@sit.fraunhofer.de


   Michael Eckel
   Fraunhofer SIT
   Rheinstrasse 75
   64295 Darmstadt
   Germany



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   Email: michael.eckel@sit.fraunhofer.de


   Shwetha Bhandari
   ThoughtSpot
   Email: shwetha.bhandari@thoughtspot.com


   Eric Voit
   Cisco Systems
   Email: evoit@cisco.com


   Bill Sulzen
   Cisco Systems
   Email: bsulzen@cisco.com


   Liang Xia (Frank)
   Huawei Technologies
   101 Software Avenue, Yuhuatai District
   Nanjing
   Jiangsu, 210012
   China
   Email: Frank.Xialiang@huawei.com


   Tom Laffey
   Hewlett Packard Enterprise
   Email: tom.laffey@hpe.com


   Guy C. Fedorkow
   Juniper Networks
   10 Technology Park Drive
   Westford
   Email: gfedorkow@juniper.net














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