Internet Engineering Task Force (IETF)                         K. WatsenRequest for Comments: 9646                               Watsen NetworksUpdates: 8572                                                 R. HousleyCategory: Standards Track                                 Vigil SecurityISSN: 2070-1721                                                S. Turner                                                                   sn3rd                                                            October 2024  Conveying a Certificate Signing Request (CSR) in a Secure Zero-Touch               Provisioning (SZTP) Bootstrapping RequestAbstract   This document extends the input to the "get-bootstrapping-data" RPC   defined in RFC 8572 to include an optional certificate signing   request (CSR), enabling a bootstrapping device to additionally obtain   an identity certificate (e.g., a Local Device Identifier (LDevID)   from IEEE 802.1AR) as part of the "onboarding information" response   provided in the RPC-reply.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available in Section 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained at   https://www.rfc-editor.org/info/rfc9646.Copyright Notice   Copyright (c) 2024 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject to BCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (https://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Revised BSD License text as described in Section 4.e of the   Trust Legal Provisions and are provided without warranty as described   in the Revised BSD License.Table of Contents   1.  Introduction     1.1.  Overview     1.2.  Terminology     1.3.  Requirements Language     1.4.  Conventions   2.  The "ietf-sztp-csr" Module     2.1.  Data Model Overview     2.2.  Example Usage     2.3.  YANG Module   3.  The "ietf-ztp-types" Module     3.1.  Data Model Overview     3.2.  YANG Module   4.  Security Considerations     4.1.  SZTP-Client Considerations       4.1.1.  Ensuring the Integrity of Asymmetric Private Keys       4.1.2.  Reuse of a Manufacturer-Generated Private Key       4.1.3.  Replay Attack Protection       4.1.4.  Connecting to an Untrusted Bootstrap Server       4.1.5.  Selecting the Best Origin Authentication Mechanism       4.1.6.  Clearing the Private Key and Associated Certificate     4.2.  SZTP-Server Considerations       4.2.1.  Verifying Proof-of-Possession       4.2.2.  Verifying Proof-of-Origin       4.2.3.  Supporting SZTP-Clients That Don't Trust the               SZTP-Server     4.3.  Security Considerations for the "ietf-sztp-csr" YANG Module     4.4.  Security Considerations for the "ietf-ztp-types" YANG           Module   5.  IANA Considerations     5.1.  The IETF XML Registry     5.2.  The YANG Module Names Registry   6.  References     6.1.  Normative References     6.2.  Informative References   Acknowledgements   Contributors   Authors' Addresses1.  Introduction1.1.  Overview   This document extends the input to the "get-bootstrapping-data" RPC   defined in [RFC8572] to include an optional certificate signing   request (CSR) [RFC2986], enabling a bootstrapping device to   additionally obtain an identity certificate (e.g., an LDevID from   [Std-802.1AR-2018]) as part of the "onboarding information" response   provided in the RPC-reply.   The ability to provision an identity certificate that is purpose-   built for a production environment during the bootstrapping process   removes reliance on the manufacturer Certification Authority (CA),   and it also enables the bootstrapped device to join the production   environment with an appropriate identity and other attributes in its   identity certificate (e.g., an LDevID).   Two YANG [RFC7950] modules are defined.  The "ietf-ztp-types" module   defines three YANG groupings for the various messages defined in this   document.  The "ietf-sztp-csr" module augments two groupings into the   "get-bootstrapping-data" RPC and defines a YANG data structure   [RFC8791] around the third grouping.1.2.  Terminology   This document uses the following terms from [RFC8572]:   *  Bootstrap Server   *  Bootstrapping Data   *  Conveyed Information   *  Device   *  Manufacturer   *  Onboarding Information   *  Signed Data   This document defines the following new terms:   SZTP-client:  The term "SZTP-client" refers to a "device" that is      using a "bootstrap server" as a source of "bootstrapping data".   SZTP-server:  The term "SZTP-server" is an alternative term for      "bootstrap server" that is symmetric with the "SZTP-client" term.1.3.  Requirements Language   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and   "OPTIONAL" in this document are to be interpreted as described in   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all   capitals, as shown here.1.4.  Conventions   Various examples in this document use "BASE64VALUE=" as a placeholder   value for binary data that has been base64 encoded (per Section 9.8   of [RFC7950]).  This placeholder value is used because real   base64-encoded structures are often many lines long and hence   distracting to the example being presented.   Various examples in this document contain long lines that may be   folded, as described in [RFC8792].2.  The "ietf-sztp-csr" Module   The "ietf-sztp-csr" module is a YANG 1.1 [RFC7950] module that   augments the "ietf-sztp-bootstrap-server" module defined in [RFC8572]   and defines a YANG "structure" that is to be conveyed in the "error-   info" node defined in Section 7.1 of [RFC8040].2.1.  Data Model Overview   The following tree diagram [RFC8340] illustrates the "ietf-sztp-csr"   module.   module: ietf-sztp-csr     augment /sztp-svr:get-bootstrapping-data/sztp-svr:input:       +---w (msg-type)?          +--:(csr-support)          |  +---w csr-support          |     +---w key-generation!          |     |  +---w supported-algorithms          |     |     +---w algorithm-identifier*   binary          |     +---w csr-generation          |        +---w supported-formats          |           +---w format-identifier*   identityref          +--:(csr)             +---w (csr-type)                +--:(p10-csr)                |  +---w p10-csr?   ct:csr                +--:(cmc-csr)                |  +---w cmc-csr?   binary                +--:(cmp-csr)                   +---w cmp-csr?   binary     structure csr-request:       +-- key-generation!       |  +-- selected-algorithm       |     +-- algorithm-identifier    binary       +-- csr-generation       |  +-- selected-format       |     +-- format-identifier    identityref       +-- cert-req-info?    ct:csr-info   The augmentation defines two kinds of parameters that an SZTP-client   can send to an SZTP-server.  The YANG structure defines one   collection of parameters that an SZTP-server can send to an SZTP-   client.   In the order of their intended use:   1.  The SZTP-client sends a "csr-support" node, encoded in a first       "get-bootstrapping-data" request to the SZTP-server, to indicate       that it supports the ability to generate CSRs.  This input       parameter conveys if the SZTP-client is able to generate a new       asymmetric key and, if so, which key algorithms it supports, as       well as what kinds of CSR structures the SZTP-client is able to       generate.   2.  The SZTP-server responds with an error, containing the "csr-       request" structure, to request the SZTP-client to generate a CSR.       This structure is used to select the key algorithm the SZTP-       client should use to generate a new asymmetric key (if       supported), the kind of CSR structure the SZTP-client should       generate, and optionally the content for the CSR itself.   3.  The SZTP-client sends one of the "*-csr" nodes, encoded in a       second "get-bootstrapping-data" request to the SZTP-server.  This       node encodes the server-requested CSR.   4.  The SZTP-server responds with onboarding information to       communicate the signed certificate to the SZTP-client.  How to do       this is discussed in Section 2.2.   To further illustrate how the augmentation and structure defined by   the "ietf-sztp-csr" module are used, below are two additional tree   diagrams showing these nodes placed where they are used.   The following tree diagram [RFC8340] illustrates SZTP's "get-   bootstrapping-data" RPC with the augmentation in place.   =============== NOTE: '\' line wrapping per RFC 8792 ================   module: ietf-sztp-bootstrap-server     rpcs:       +---x get-bootstrapping-data          +---w input          |  +---w signed-data-preferred?          empty          |  +---w hw-model?                       string          |  +---w os-name?                        string          |  +---w os-version?                     string          |  +---w nonce?                          binary          |  +---w (sztp-csr:msg-type)?          |     +--:(sztp-csr:csr-support)          |     |  +---w sztp-csr:csr-support          |     |     +---w sztp-csr:key-generation!          |     |     |  +---w sztp-csr:supported-algorithms          |     |     |     +---w sztp-csr:algorithm-identifier*   bina\   ry          |     |     +---w sztp-csr:csr-generation          |     |        +---w sztp-csr:supported-formats          |     |           +---w sztp-csr:format-identifier*   identit\   yref          |     +--:(sztp-csr:csr)          |        +---w (sztp-csr:csr-type)          |           +--:(sztp-csr:p10-csr)          |           |  +---w sztp-csr:p10-csr?   ct:csr          |           +--:(sztp-csr:cmc-csr)          |           |  +---w sztp-csr:cmc-csr?   binary          |           +--:(sztp-csr:cmp-csr)          |              +---w sztp-csr:cmp-csr?   binary          +--ro output             +--ro reporting-level?    enumeration {onboarding-server}?             +--ro conveyed-information    cms             +--ro owner-certificate?      cms             +--ro ownership-voucher?      cms   The following tree diagram [RFC8340] illustrates RESTCONF's "errors"   RPC-reply message with the "csr-request" structure in place.   module: ietf-restconf     +--ro errors        +--ro error* []           +--ro error-type       enumeration           +--ro error-tag        string           +--ro error-app-tag?   string           +--ro error-path?      instance-identifier           +--ro error-message?   string           +--ro error-info              +--ro sztp-csr:csr-request                 +--ro sztp-csr:key-generation!                 |  +--ro sztp-csr:selected-algorithm                 |     +--ro sztp-csr:algorithm-identifier    binary                 +--ro sztp-csr:csr-generation                 |  +--ro sztp-csr:selected-format                 |     +--ro sztp-csr:format-identifier    identityref                 +--ro sztp-csr:cert-req-info?    ct:csr-info2.2.  Example Usage      |  NOTE: The examples below are encoded using JSON, but they could      |  equally well be encoded using XML, as is supported by SZTP.   An SZTP-client implementing this specification would signal to the   bootstrap server its willingness to generate a CSR by including the   "csr-support" node in its "get-bootstrapping-data" RPC.  In the   example below, the SZTP-client additionally indicates that it is able   to generate keys and provides a list of key algorithms it supports,   as well as provide a list of certificate formats it supports.   REQUEST   =============== NOTE: '\' line wrapping per RFC 8792 ================   POST /restconf/operations/ietf-sztp-bootstrap-server:get-bootstrappi\   ng-data HTTP/1.1   HOST: example.com   Content-Type: application/yang-data+json   {     "ietf-sztp-bootstrap-server:input" : {       "hw-model": "model-x",       "os-name": "vendor-os",       "os-version": "17.3R2.1",       "nonce": "extralongbase64encodedvalue=",       "ietf-sztp-csr:csr-support": {         "key-generation": {           "supported-algorithms": {             "algorithm-identifier": [               "BASE64VALUE1",               "BASE64VALUE2",               "BASE64VALUE3"             ]           }         },         "csr-generation": {           "supported-formats": {             "format-identifier": [               "ietf-ztp-types:p10-csr",               "ietf-ztp-types:cmc-csr",               "ietf-ztp-types:cmp-csr"             ]           }         }       }     }   }   Assuming the SZTP-server wishes to prompt the SZTP-client to provide   a CSR, then it would respond with an HTTP 400 Bad Request error code.   In the example below, the SZTP-server specifies that it wishes the   SZTP-client to generate a key using a specific algorithm and generate   a PKCS#10-based CSR containing specific content.   RESPONSE   HTTP/1.1 400 Bad Request   Date: Sat, 31 Oct 2021 17:02:40 GMT   Server: example-server   Content-Type: application/yang-data+json   {     "ietf-restconf:errors" : {       "error" : [         {           "error-type": "application",           "error-tag": "missing-attribute",           "error-message": "Missing input parameter",           "error-info": {             "ietf-sztp-csr:csr-request": {               "key-generation": {                 "selected-algorithm": {                   "algorithm-identifier": "BASE64VALUE="                 }               },               "csr-generation": {                 "selected-format": {                   "format-identifier": "ietf-ztp-types:p10-csr"                 }               },               "cert-req-info": "BASE64VALUE="             }           }         }       ]     }   }   Upon being prompted to provide a CSR, the SZTP-client would POST   another "get-bootstrapping-data" request but this time including one   of the "csr" nodes to convey its CSR to the SZTP-server:   REQUEST   =============== NOTE: '\' line wrapping per RFC 8792 ================   POST /restconf/operations/ietf-sztp-bootstrap-server:get-bootstrappi\   ng-data HTTP/1.1   HOST: example.com   Content-Type: application/yang-data+json   {     "ietf-sztp-bootstrap-server:input" : {       "hw-model": "model-x",       "os-name": "vendor-os",       "os-version": "17.3R2.1",       "nonce": "extralongbase64encodedvalue=",       "ietf-sztp-csr:p10-csr": "BASE64VALUE="     }   }   At this point, it is expected that the SZTP-server, perhaps in   conjunction with other systems, such as a backend CA or registration   authority (RA), will validate the CSR's origin and proof-of-   possession and, assuming the CSR is approved, issue a signed   certificate for the bootstrapping device.   The SZTP-server responds with conveyed information (the "conveyed-   information" node shown below) that encodes "onboarding-information"   (inside the base64 value) containing a signed identity certificate   for the CSR provided by the SZTP-client:   RESPONSE   HTTP/1.1 200 OK   Date: Sat, 31 Oct 2021 17:02:40 GMT   Server: example-server   Content-Type: application/yang-data+json   {     "ietf-sztp-bootstrap-server:output" : {       "reporting-level": "verbose",       "conveyed-information": "BASE64VALUE="     }   }   How the signed certificate is conveyed inside the onboarding   information is outside the scope of this document.  Some   implementations may choose to convey it inside a script (e.g., SZTP's   "pre-configuration-script"), while other implementations may choose   to convey it inside the SZTP "configuration" node.  SZTP onboarding   information is described in Section 2.2 of [RFC8572].   Below are two examples of conveying the signed certificate inside the   "configuration" node.  Both examples assume that the SZTP-client   understands the "ietf-keystore" module defined in [RFC9642].   This first example illustrates the case where the signed certificate   is for the same asymmetric key used by the SZTP-client's   manufacturer-generated identity certificate (e.g., an Initial Device   Identifier (IDevID) from [Std-802.1AR-2018]).  As such, the   configuration needs to associate the newly signed certificate with   the existing asymmetric key:   =============== NOTE: '\' line wrapping per RFC 8792 ================   {     "ietf-keystore:keystore": {       "asymmetric-keys": {         "asymmetric-key": [           {             "name": "Manufacturer-Generated Hidden Key",             "public-key-format": "ietf-crypto-types:subject-public-key\   -info-format",             "public-key": "BASE64VALUE=",             "hidden-private-key": [null],             "certificates": {               "certificate": [                 {                   "name": "Manufacturer-Generated IDevID Cert",                   "cert-data": "BASE64VALUE="                 },                 {                   "name": "Newly-Generated LDevID Cert",                   "cert-data": "BASE64VALUE="                 }               ]             }           }         ]       }     }   }   This second example illustrates the case where the signed certificate   is for a newly generated asymmetric key.  As such, the configuration   needs to associate the newly signed certificate with the newly   generated asymmetric key:   =============== NOTE: '\' line wrapping per RFC 8792 ================   {     "ietf-keystore:keystore": {       "asymmetric-keys": {         "asymmetric-key": [           {             "name": "Manufacturer-Generated Hidden Key",             "public-key-format": "ietf-crypto-types:subject-public-key\   -info-format",             "public-key": "BASE64VALUE=",             "hidden-private-key": [null],             "certificates": {               "certificate": [                 {                   "name": "Manufacturer-Generated IDevID Cert",                   "cert-data": "BASE64VALUE="                 }               ]             }           },           {             "name": "Newly-Generated Hidden Key",             "public-key-format": "ietf-crypto-types:subject-public-key\   -info-format",             "public-key": "BASE64VALUE=",             "hidden-private-key": [null],             "certificates": {               "certificate": [                 {                   "name": "Newly-Generated LDevID Cert",                   "cert-data": "BASE64VALUE="                 }               ]             }           }         ]       }     }   }   In addition to configuring the signed certificate, it is often   necessary to also configure the issuer's signing certificate so that   the device (i.e., STZP-client) can authenticate certificates   presented by peer devices signed by the same issuer as its own.   While outside the scope of this document, one way to do this would be   to use the "ietf-truststore" module defined in [RFC9641].2.3.  YANG Module   This module augments an RPC defined in [RFC8572].  The module uses   data types and groupings defined in [RFC8572], [RFC8791], and   [RFC9640].  The module also has an informative reference to   [Std-802.1AR-2018].   <CODE BEGINS> file "ietf-sztp-csr@2024-10-10.yang"   module ietf-sztp-csr {     yang-version 1.1;     namespace "urn:ietf:params:xml:ns:yang:ietf-sztp-csr";     prefix sztp-csr;     import ietf-sztp-bootstrap-server {       prefix sztp-svr;       reference         "RFC 8572: Secure Zero Touch Provisioning (SZTP)";     }     import ietf-yang-structure-ext {       prefix sx;       reference         "RFC 8791: YANG Data Structure Extensions";     }     import ietf-ztp-types {       prefix zt;       reference         "RFC 9646: Conveying a Certificate Signing Request (CSR)                    in a Secure Zero-Touch Provisioning (SZTP)                    Bootstrapping Request";     }     organization       "IETF NETCONF (Network Configuration) Working Group";     contact       "WG Web:   https://datatracker.ietf.org/wg/netconf        WG List:  NETCONF WG list <mailto:netconf@ietf.org>        Authors:  Kent Watsen <mailto:kent+ietf@watsen.net>                  Russ Housley <mailto:housley@vigilsec.com>                  Sean Turner <mailto:sean@sn3rd.com>";     description       "This module augments the 'get-bootstrapping-data' RPC,        defined in the 'ietf-sztp-bootstrap-server' module from        SZTP (RFC 8572), enabling the SZTP-client to obtain a        signed identity certificate (e.g., an LDevID from IEEE        802.1AR) as part of the SZTP onboarding information        response.        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',        'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',        'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this        document are to be interpreted as described in BCP 14        (RFC 2119) (RFC 8174) when, and only when, they appear        in all capitals, as shown here.        Copyright (c) 2024 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 9646        (https://www.rfc-editor.org/info/rfc9646); see the        RFC itself for full legal notices.";     revision 2024-10-10 {       description         "Initial version.";       reference         "RFC 9646: Conveying a Certificate Signing Request (CSR)                    in a Secure Zero-Touch Provisioning (SZTP)                    Bootstrapping Request";     }     // Protocol-accessible nodes     augment "/sztp-svr:get-bootstrapping-data/sztp-svr:input" {       description         "This augmentation adds the 'csr-support' and 'csr' nodes to          the SZTP (RFC 8572) 'get-bootstrapping-data' request message,          enabling the SZTP-client to obtain an identity certificate          (e.g., an LDevID from IEEE 802.1AR) as part of the onboarding          information response provided by the SZTP-server.          The 'csr-support' node enables the SZTP-client to indicate          that it supports generating certificate signing requests          (CSRs) and to provide details around the CSRs it is able          to generate.          The 'csr' node enables the SZTP-client to relay a CSR to          the SZTP-server.";       reference         "IEEE 802.1AR: IEEE Standard for Local and Metropolitan                        Area Networks - Secure Device Identity          RFC 8572: Secure Zero Touch Provisioning (SZTP)";       choice msg-type {         description           "Messages are mutually exclusive.";         case csr-support {           description             "Indicates how the SZTP-client supports generating CSRs.              If present and a SZTP-server wishes to request the              SZTP-client generate a CSR, the SZTP-server MUST              respond with an HTTP 400 Bad Request error code with an              'ietf-restconf:errors' message having the 'error-tag'              value 'missing-attribute' and the 'error-info' node              containing the 'csr-request' structure described              in this module.";           uses zt:csr-support-grouping;         }         case csr {           description             "Provides the CSR generated by the SZTP-client.              When present, the SZTP-server SHOULD respond with              an SZTP onboarding information message containing              a signed certificate for the conveyed CSR.  The              SZTP-server MAY alternatively respond with another              HTTP error containing another 'csr-request'; in              which case, the SZTP-client MUST delete any key              generated for the previously generated CSR.";           uses zt:csr-grouping;         }       }     }     sx:structure csr-request {       description         "A YANG data structure, per RFC 8791, that specifies          details for the CSR that the ZTP-client is to generate.";       reference         "RFC 8791: YANG Data Structure Extensions";       uses zt:csr-request-grouping;     }   }   <CODE ENDS>3.  The "ietf-ztp-types" Module   This section defines a YANG 1.1 [RFC7950] module that defines three   YANG groupings, one for each message sent between a ZTP-client and   ZTP-server.  This module is defined independently of the "ietf-sztp-   csr" module so that its groupings may be used by bootstrapping   protocols other than SZTP [RFC8572].3.1.  Data Model Overview   The following tree diagram [RFC8340] illustrates the three groupings   defined in the "ietf-ztp-types" module.   module: ietf-ztp-types     grouping csr-support-grouping       +-- csr-support          +-- key-generation!          |  +-- supported-algorithms          |     +-- algorithm-identifier*   binary          +-- csr-generation             +-- supported-formats                +-- format-identifier*   identityref     grouping csr-request-grouping       +-- key-generation!       |  +-- selected-algorithm       |     +-- algorithm-identifier    binary       +-- csr-generation       |  +-- selected-format       |     +-- format-identifier    identityref       +-- cert-req-info?    ct:csr-info     grouping csr-grouping       +-- (csr-type)          +--:(p10-csr)          |  +-- p10-csr?   ct:csr          +--:(cmc-csr)          |  +-- cmc-csr?   binary          +--:(cmp-csr)             +-- cmp-csr?   binary3.2.  YANG Module   This module uses data types and groupings defined in [RFC8791] and   [RFC9640].  The module has additional normative references to   [RFC2986], [RFC4210], [RFC5272], and [ITU.X690.2021] and an   informative reference to [Std-802.1AR-2018].   <CODE BEGINS> file "ietf-ztp-types@2024-10-10.yang"   module ietf-ztp-types {     yang-version 1.1;     namespace "urn:ietf:params:xml:ns:yang:ietf-ztp-types";     prefix zt;     import ietf-crypto-types {       prefix ct;       reference         "RFC 9640: YANG Data Types and Groupings for Cryptography";     }     organization       "IETF NETCONF (Network Configuration) Working Group";     contact       "WG Web:   https://datatracker.ietf.org/wg/netconf        WG List:  NETCONF WG list <mailto:netconf@ietf.org>        Authors:  Kent Watsen <mailto:kent+ietf@watsen.net>                  Russ Housley <mailto:housley@vigilsec.com>                  Sean Turner <mailto:sean@sn3rd.com>";     description       "This module defines three groupings that enable        bootstrapping devices to 1) indicate if and how they        support generating CSRs, 2) obtain a request to        generate a CSR, and 3) communicate the requested CSR.        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',        'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',        'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this        document are to be interpreted as described in BCP 14        (RFC 2119) (RFC 8174) when, and only when, they appear        in all capitals, as shown here.        Copyright (c) 2024 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 9646        (https://www.rfc-editor.org/info/rfc9646); see the        RFC itself for full legal notices.";     revision 2024-10-10 {       description         "Initial version.";       reference         "RFC 9646: Conveying a Certificate Signing Request (CSR)                    in a Secure Zero-Touch Provisioning (SZTP)                    Bootstrapping Request";     }     identity certificate-request-format {       description         "A base identity for the request formats supported          by the ZTP-client.          Additional derived identities MAY be defined by          future efforts.";     }     identity p10-csr {       base certificate-request-format;       description         "Indicates that the ZTP-client supports generating          requests using the 'CertificationRequest' structure          defined in RFC 2986.";       reference         "RFC 2986: PKCS #10: Certification Request Syntax                    Specification Version 1.7";     }     identity cmp-csr {       base certificate-request-format;       description         "Indicates that the ZTP-client supports generating          requests using a profiled version of the PKIMessage          that MUST contain a PKIHeader followed by a PKIBody          containing only the ir, cr, kur, or p10cr structures          defined in RFC 4210.";       reference         "RFC 4210: Internet X.509 Public Key Infrastructure                    Certificate Management Protocol (CMP)";     }     identity cmc-csr {       base certificate-request-format;       description         "Indicates that the ZTP-client supports generating          requests using a profiled version of the 'Full          PKI Request' structure defined in RFC 5272.";       reference         "RFC 5272: Certificate Management over CMS (CMC)";     }     // Protocol-accessible nodes     grouping csr-support-grouping {       description         "A grouping enabling use by other efforts.";       container csr-support {         description           "Enables a ZTP-client to indicate that it supports            generating certificate signing requests (CSRs) and            provides details about the CSRs it is able to            generate.";         container key-generation {           presence "Indicates that the ZTP-client is capable of                     generating a new asymmetric key pair.                     If this node is not present, the ZTP-server MAY                     request a CSR using the asymmetric key associated                     with the device's existing identity certificate                     (e.g., an IDevID from IEEE 802.1AR).";           description             "Specifies details for the ZTP-client's ability to              generate a new asymmetric key pair.";           container supported-algorithms {             description               "A list of public key algorithms supported by the                ZTP-client for generating a new asymmetric key.";             leaf-list algorithm-identifier {               type binary;               min-elements 1;               description                 "An AlgorithmIdentifier, as defined in RFC 2986,                  encoded using ASN.1 Distinguished Encoding Rules                  (DER), as specified in ITU-T X.690.";               reference                 "RFC 2986: PKCS #10: Certification Request Syntax                            Specification Version 1.7                  ITU-T X.690:                    Information technology - ASN.1 encoding rules:                    Specification of Basic Encoding Rules (BER),                    Canonical Encoding Rules (CER) and Distinguished                    Encoding Rules (DER)";             }           }         }         container csr-generation {           description             "Specifies details for the ZTP-client's ability to              generate certificate signing requests.";           container supported-formats {             description               "A list of certificate request formats supported                by the ZTP-client for generating a new key.";             leaf-list format-identifier {               type identityref {                 base zt:certificate-request-format;               }               min-elements 1;               description                 "A certificate request format supported by the                  ZTP-client.";             }           }         }       }     }     grouping csr-request-grouping {       description         "A grouping enabling use by other efforts.";       container key-generation {         presence "Provided by a ZTP-server to indicate that it wishes                   the ZTP-client to generate a new asymmetric key.                   This statement is present so the mandatory                   descendant nodes do not imply that this node must                   be configured.";         description           "The key generation parameters selected by the ZTP-server.            This leaf MUST only appear if the ZTP-client's            'csr-support' included the 'key-generation' node.";         container selected-algorithm {           description             "The key algorithm selected by the ZTP-server.  The              algorithm MUST be one of the algorithms specified by              the 'supported-algorithms' node in the ZTP-client's              message containing the 'csr-support' structure.";           leaf algorithm-identifier {             type binary;             mandatory true;             description               "An AlgorithmIdentifier, as defined in RFC 2986,                encoded using ASN.1 Distinguished Encoding Rules                (DER), as specified in ITU-T X.690.";             reference               "RFC 2986: PKCS #10: Certification Request Syntax                          Specification Version 1.7                ITU-T X.690:                  Information technology - ASN.1 encoding rules:                  Specification of Basic Encoding Rules (BER),                  Canonical Encoding Rules (CER) and Distinguished                  Encoding Rules (DER)";           }         }       }       container csr-generation {         description           "Specifies details for the CSR that the ZTP-client            is to generate.";         container selected-format {           description             "The CSR format selected by the ZTP-server.  The              format MUST be one of the formats specified by              the 'supported-formats' node in the ZTP-client's              request message.";           leaf format-identifier {             type identityref {               base zt:certificate-request-format;             }             mandatory true;             description               "A certificate request format to be used by the                ZTP-client.";           }         }       }       leaf cert-req-info {         type ct:csr-info;         description           "A CertificationRequestInfo structure, as defined in            RFC 2986, and modeled via a 'typedef' statement by            RFC 9640.            Enables the ZTP-server to provide a fully populated            CertificationRequestInfo structure that the ZTP-client            only needs to sign in order to generate the complete            'CertificationRequest' structure to send to the ZTP-server            in its next 'get-bootstrapping-data' request message.            When provided, the ZTP-client MUST use this structure            to generate its CSR; failure to do so will result in a            400 Bad Request response containing another 'csr-request'            structure.            When not provided, the ZTP-client SHOULD generate a CSR            using the same structure defined in its existing identity            certificate (e.g., an IDevID from IEEE 802.1AR).            If the 'AlgorithmIdentifier' field contained inside the            certificate 'SubjectPublicKeyInfo' field does not match            the algorithm identified by the 'selected-algorithm' node,            then the client MUST reject the certificate and raise an            error.";         reference           "RFC 2986:              PKCS #10: Certification Request Syntax Specification              Version 1.7            RFC 9640:              YANG Data Types and Groupings for Cryptography";       }     }     grouping csr-grouping {       description         "Enables a ZTP-client to convey a certificate signing          request, using the encoding format selected by a          ZTP-server's 'csr-request' response to the ZTP-client's          previously sent request containing the 'csr-support'          node.";       choice csr-type {         mandatory true;         description           "A choice amongst certificate signing request formats.            Additional formats MAY be augmented into this 'choice'            statement by future efforts.";         case p10-csr {           leaf p10-csr {             type ct:p10-csr;             description               "A CertificationRequest structure, per RFC 2986.                Encoding details are defined in the 'ct:csr'                typedef defined in RFC 9640.                A raw P10 does not support origin authentication in                the CSR structure.  External origin authentication                may be provided via the ZTP-client's authentication                to the ZTP-server at the transport layer (e.g., TLS).";             reference               "RFC 2986: PKCS #10: Certification Request Syntax                          Specification Version 1.7                RFC 9640: YANG Data Types and Groupings for                          Cryptography";           }         }         case cmc-csr {           leaf cmc-csr {             type binary;             description               "A profiled version of the 'Full PKI Request'                message defined in RFC 5272, encoded using ASN.1                Distinguished Encoding Rules (DER), as specified                in ITU-T X.690.                For asymmetric-key-based origin authentication of a                CSR based on the initial device identity certificate's                private key for the associated identity certificate's                public key, the PKIData contains one reqSequence                element and no cmsSequence or otherMsgSequence                elements.  The reqSequence is the TaggedRequest,                and it is the tcr CHOICE branch.  The tcr is the                TaggedCertificationRequest, and it is the bodyPartID                and the certificateRequest elements.  The                certificateRequest is signed with the initial device                identity certificate's private key.  The initial device                identity certificate, and optionally its certificate                chain is included in the SignedData certificates that                encapsulate the PKIData.                For asymmetric-key-based origin authentication based on                the initial device identity certificate's private key                that signs the encapsulated CSR signed by the local                device identity certificate's private key, the                PKIData contains one cmsSequence element and no                reqSequence or otherMsgSequence                elements.  The cmsSequence is the TaggedContentInfo,                and it includes a bodyPartID element and a contentInfo.                The contentInfo is a SignedData encapsulating a PKIData                with one reqSequence element and no cmsSequence or                otherMsgSequence elements.  The reqSequence is the                TaggedRequest, and it is the tcr CHOICE.  The tcr is the                TaggedCertificationRequest, and it is the bodyPartID and                the certificateRequest elements.  PKIData contains one                cmsSequence element and no controlSequence, reqSequence,                or otherMsgSequence elements.  The certificateRequest                is signed with the local device identity certificate's                private key.  The initial device identity certificate                and optionally its certificate chain is included in                the SignedData certificates that encapsulate the                PKIData.                For shared-secret-based origin authentication of a                CSR signed by the local device identity certificate's                private key, the PKIData contains one cmsSequence                element and no reqSequence or otherMsgSequence                elements.  The cmsSequence is the TaggedContentInfo,                and it includes a bodyPartID element and a contentInfo.                The contentInfo is an AuthenticatedData encapsulating                a PKIData with one reqSequence element and no                cmsSequences or otherMsgSequence elements.  The                reqSequence is the TaggedRequest, and it is the tcr                CHOICE.  The tcr is the TaggedCertificationRequest,                and it is the bodyPartID and the certificateRequest                elements.  The certificateRequest is signed with the                local device identity certificate's private key.  The                initial device identity certificate and optionally its                certificate chain is included in the SignedData                certificates that encapsulate the PKIData.";             reference               "RFC 5272: Certificate Management over CMS (CMC)                ITU-T X.690:                  Information technology - ASN.1 encoding rules:                  Specification of Basic Encoding Rules (BER),                  Canonical Encoding Rules (CER) and Distinguished                  Encoding Rules (DER)";           }         }         case cmp-csr {           leaf cmp-csr {             type binary;             description               "A PKIMessage structure, as defined in RFC 4210,                encoded using ASN.1 Distinguished Encoding Rules                (DER), as specified in ITU-T X.690.                For asymmetric-key-based origin authentication of a                CSR based on the initial device identity certificate's                private key for the associated initial device identity                certificate's public key, PKIMessages contain one                PKIMessage with the header and body elements, do not                contain a protection element, and SHOULD contain the                extraCerts element.  The header element contains the                pvno, sender, and recipient elements.  The pvno contains                cmp2000, and the sender contains the subject of the                initial device identity certificate. The body element                contains an ir, cr, kur, or p10cr CHOICE of type                CertificationRequest.  It is signed with the initial                device identity certificate's private key.  The                extraCerts element contains the initial device identity                certificate, optionally followed by its certificate                chain excluding the trust anchor.                For asymmetric-key-based origin authentication based                on the initial device identity certificate's private                key that signs the encapsulated CSR signed by the local                device identity certificate's private key, PKIMessages                contain one PKIMessage with the header, body, and                protection elements and SHOULD contain the extraCerts                element.  The header element contains the pvno, sender,                recipient, protectionAlg, and optionally senderKID                elements.  The pvno contains cmp2000, the sender                contains the subject of the initial device identity                certificate, the protectionAlg contains the                AlgorithmIdentifier of the used signature algorithm,                and the senderKID contains the subject key identifier                of the initial device identity certificate. The body                element contains an ir, cr, kur, or p10cr CHOICE of                type CertificationRequest.  It is signed with the local                device identity certificate's private key.  The                protection element contains the digital signature                generated with the initial device identity                certificate's private key.  The extraCerts element                contains the initial device identity certificate,                optionally followed by its certificate chain excluding                the trust anchor.                For shared-secret-based origin authentication of a                CSR signed by the local device identity certificate's                private key, PKIMessages contain one PKIMessage with                the header, body, and protection element and no                extraCerts element.  The header element contains the                pvno, sender, recipient, protectionAlg, and senderKID                elements.  The pvno contains cmp2000, the protectionAlg                contains the AlgorithmIdentifier of the used Message                Authentication Code (MAC) algorithm, and the senderKID                contains a reference the recipient can use to identify                the shared secret.  The body element contains an ir, cr,                kur, or p10cr CHOICE of type CertificationRequest.  It                is signed with the local device identity certificate's                private key.  The protection element contains the MAC                value generated with the shared secret.";             reference               "RFC 4210:                  Internet X.509 Public Key Infrastructure                  Certificate Management Protocol (CMP)                ITU-T X.690:                  Information technology - ASN.1 encoding rules:                  Specification of Basic Encoding Rules (BER),                  Canonical Encoding Rules (CER) and Distinguished                  Encoding Rules (DER)";           }         }       }     }   }   <CODE ENDS>4.  Security Considerations   This document builds on top of the solution presented in [RFC8572],   and therefore all the security considerations discussed in [RFC8572]   apply here as well.   For the various CSR formats, when using PKCS#10, the security   considerations in [RFC2986] apply; when using CMP, the security   considerations in [RFC4210] apply; and when using CMC, the security   considerations in [RFC5272] apply.   For the various authentication mechanisms, when using TLS-level   authentication, the security considerations in [RFC8446] apply, and   when using HTTP-level authentication, the security considerations in   [RFC9110] apply.4.1.  SZTP-Client Considerations4.1.1.  Ensuring the Integrity of Asymmetric Private Keys   The private key the SZTP-client uses for the dynamically generated   identity certificate MUST be protected from inadvertent disclosure in   order to prevent identity fraud.   The security of this private key is essential in order to ensure the   associated identity certificate can be used to authenticate the   device it is issued to.   It is RECOMMENDED that devices are manufactured with a hardware   security module (HSM), such as a trusted platform module (TPM), to   generate and contain the private key within the security perimeter of   the HSM.  In such cases, the private key and its associated   certificates MAY have long validity periods.   In cases where the SZTP-client does not possess an HSM or is unable   to use an HSM to protect the private key, it is RECOMMENDED to   periodically reset the private key (and associated identity   certificates) in order to minimize the lifetime of unprotected   private keys.  For instance, a Network Management System (NMS)   controller/orchestrator application could periodically prompt the   SZTP-client to generate a new private key and provide a certificate   signing request (CSR) or, alternatively, push both the key and an   identity certificate to the SZTP-client using, e.g., a PKCS#12   message [RFC7292].  In another example, the SZTP-client could be   configured to periodically reset the configuration to its factory   default, thus causing removal of the private key and associated   identity certificates and re-execution of the SZTP protocol.4.1.2.  Reuse of a Manufacturer-Generated Private Key   It is RECOMMENDED that a new private key is generated for each CSR   described in this document.   Implementations must randomly generate nonces and private keys.  The   use of inadequate pseudorandom number generators (PRNGs) to generate   cryptographic keys can result in little or no security.  An attacker   may find it much easier to reproduce the PRNG environment that   produced the keys, searching the resulting small set of   possibilities, rather than brute force searching the whole key space.   As an example of predictable random numbers, see CVE-2008-0166   [CVE-2008-0166], and some consequences of low-entropy random numbers   are discussed in "Mining Your Ps and Qs" [MiningPsQs].  The   generation of quality random numbers is difficult.  [ISO.20543-2019],   [NIST.SP.800-90Ar1], BSI AIS 31 [AIS31], BCP 106 [RFC4086], and   others offer valuable guidance in this area.   This private key SHOULD be protected as well as the built-in private   key associated with the SZTP-client's initial device identity   certificate (e.g., the IDevID from [Std-802.1AR-2018]).   In cases where it is not possible to generate a new private key that   is protected as well as the built-in private key, it is RECOMMENDED   to reuse the built-in private key rather than generate a new private   key that is not as well protected.4.1.3.  Replay Attack Protection   This RFC enables an SZTP-client to announce an ability to generate a   new key to use for its CSR.   When the SZTP-server responds with a request for the SZTP-client to   generate a new key, it is essential that the SZTP-client actually   generates a new key.   Generating a new key each time enables the random bytes used to   create the key to also serve the dual-purpose of acting like a   "nonce" used in other mechanisms to detect replay attacks.   When a fresh public/private key pair is generated for the request,   confirmation to the SZTP-client that the response has not been   replayed is enabled by the SZTP-client's fresh public key appearing   in the signed certificate provided by the SZTP-server.   When a public/private key pair associated with the manufacturer-   generated identity certificate (e.g., IDevID) is used for the   request, there may not be confirmation to the SZTP-client that the   response has not been replayed; however, the worst case result is a   lost certificate that is associated to the private key known only to   the SZTP-client.  Protection of the private-key information is vital   to public-key cryptography.  Disclosure of the private-key material   to another entity can lead to masquerades.4.1.4.  Connecting to an Untrusted Bootstrap Server   [RFC8572] allows SZTP-clients to connect to untrusted SZTP-servers by   blindly authenticating the SZTP-server's TLS end-entity certificate.   As is discussed in Section 9.5 of [RFC8572], in such cases, the SZTP-   client MUST assert that the bootstrapping data returned is signed if   the SZTP-client is to trust it.   However, the HTTP error message used in this document cannot be   signed data, as described in [RFC8572].   Therefore, the solution presented in this document cannot be used   when the SZTP-client connects to an untrusted SZTP-server.   Consistent with the recommendation presented in Section 9.6 of   [RFC8572], SZTP-clients SHOULD NOT pass the "csr-support" input   parameter to an untrusted SZTP-server.  SZTP-clients SHOULD instead   pass the "signed-data-preferred" input parameter, as discussed in   Appendix B of [RFC8572].4.1.5.  Selecting the Best Origin Authentication Mechanism   The origin of the CSR must be verified before a certificate is   issued.   When generating a new key, it is important that the SZTP-client be   able to provide additional proof that it was the entity that   generated the key.   The CMP and CMC certificate request formats defined in this document   support origin authentication.  A raw PKCS#10 CSR does not support   origin authentication.   The CMP and CMC request formats support origin authentication using   both PKI and a shared secret.   Typically, only one possible origin authentication mechanism can   possibly be used, but in the case that the SZTP-client authenticates   itself using both TLS-level (e.g., IDevID) and HTTP-level credentials   (e.g., Basic), as is allowed by Section 5.3 of [RFC8572], then the   SZTP-client may need to choose between the two options.   In the case that the SZTP-client must choose between an asymmetric   key option versus a shared secret for origin authentication, it is   RECOMMENDED that the SZTP-client choose using the asymmetric key.4.1.6.  Clearing the Private Key and Associated Certificate   Unlike a manufacturer-generated identity certificate (e.g., IDevID),   the deployment-generated identity certificate (e.g., LDevID) and the   associated private key (assuming a new private key was generated for   the purpose) are considered user data and SHOULD be cleared whenever   the SZTP-client is reset to its factory default state, such as by the   "factory-reset" RPC defined in [RFC8808].4.2.  SZTP-Server Considerations4.2.1.  Verifying Proof-of-Possession   Regardless, if using a new asymmetric key or the bootstrapping   device's manufacturer-generated key (e.g., the IDevID key), the   public key is placed in the CSR and the CSR is signed by that private   key.  Proof-of-possession of the private key is verified by ensuring   the signature over the CSR using the public key placed in the CSR.4.2.2.  Verifying Proof-of-Origin   When the bootstrapping device's manufacturer-generated private key   (e.g., the IDevID key) is reused for the CSR, proof-of-origin is   verified by validating the IDevID-issuer cert and ensuring that the   CSR uses the same key pair.   When the bootstrapping device's manufacturer-generated private key   (e.g., an IDevID key from IEEE 802.1AR) is reused for the CSR, proof-   of-origin is verified by validating the IDevID certification path and   ensuring that the CSR uses the same key pair.   When a fresh asymmetric key is used with the CMP or CMC formats, the   authentication is part of the protocols, which could employ either   the manufacturer-generated private key or a shared secret.  In   addition, CMP and CMC support processing by an RA before the request   is passed to the CA, which allows for more robust handling of errors.4.2.3.  Supporting SZTP-Clients That Don't Trust the SZTP-Server   [RFC8572] allows SZTP-clients to connect to untrusted SZTP-servers by   blindly authenticating the SZTP-server's TLS end-entity certificate.   As is recommended in Section 4.1.4 of this document, in such cases,   SZTP-clients SHOULD pass the "signed-data-preferred" input parameter.   The reciprocal of this statement is that SZTP-servers, wanting to   support SZTP-clients that don't trust them, SHOULD support the   "signed-data-preferred" input parameter, as discussed in Appendix B   of [RFC8572].4.3.  Security Considerations for the "ietf-sztp-csr" YANG Module   The recommended format for documenting the security considerations   for YANG modules is described in Section 3.7 of [RFC8407].  However,   this module only augments two input parameters into the "get-   bootstrapping-data" RPC in [RFC8572] and therefore only needs to   point to the relevant Security Considerations sections in that RFC.   *  Security considerations for the "get-bootstrapping-data" RPC are      described in Section 9.16 of [RFC8572].   *  Security considerations for the "input" parameters passed inside      the "get-bootstrapping-data" RPC are described in Section 9.6 of      [RFC8572].4.4.  Security Considerations for the "ietf-ztp-types" YANG Module   The recommended format for documenting the security considerations   for YANG modules is described in Section 3.7 of [RFC8407].  However,   this module does not define any protocol-accessible nodes (it only   defines "identity" and "grouping" statements), and therefore there   are no security considerations to report.5.  IANA Considerations5.1.  The IETF XML Registry   IANA has registered two URIs in the "ns" registry of the "IETF XML   Registry" [RFC3688] maintained at <https://www.iana.org/assignments/   xml-registry/>.   URI:  urn:ietf:params:xml:ns:yang:ietf-sztp-csr   Registrant Contact:  The NETCONF WG of the IETF.   XML:  N/A; the requested URI is an XML namespace.   URI:  urn:ietf:params:xml:ns:yang:ietf-ztp-types   Registrant Contact:  The NETCONF WG of the IETF.   XML:  N/A; the requested URI is an XML namespace.5.2.  The YANG Module Names Registry   IANA has registered two YANG modules in the "YANG Module Names"   registry [RFC6020] maintained at <https://www.iana.org/assignments/   yang-parameters/>.   Name:  ietf-sztp-csr   Namespace:  urn:ietf:params:xml:ns:yang:ietf-sztp-csr   Prefix:  sztp-csr   Reference:  RFC 9646   Name:  ietf-ztp-types   Namespace:  urn:ietf:params:xml:ns:yang:ietf-ztp-types   Prefix:  ztp-types   Reference:  RFC 96466.  References6.1.  Normative References   [ITU.X690.2021]              ITU, "Information technology - ASN.1 encoding rules:              Specification of Basic Encoding Rules (BER), Canonical              Encoding Rules (CER) and Distinguished Encoding Rules              (DER)", ITU-T Recommendation X.690, ISO/IEC 8825-1,              February 2021, <https://www.itu.int/rec/T-REC-X.690/>.   [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>.   [RFC2986]  Nystrom, M. and B. Kaliski, "PKCS #10: Certification              Request Syntax Specification Version 1.7", RFC 2986,              DOI 10.17487/RFC2986, November 2000,              <https://www.rfc-editor.org/info/rfc2986>.   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,              DOI 10.17487/RFC3688, January 2004,              <https://www.rfc-editor.org/info/rfc3688>.   [RFC4210]  Adams, C., Farrell, S., Kause, T., and T. Mononen,              "Internet X.509 Public Key Infrastructure Certificate              Management Protocol (CMP)", RFC 4210,              DOI 10.17487/RFC4210, September 2005,              <https://www.rfc-editor.org/info/rfc4210>.   [RFC5272]  Schaad, J. and M. Myers, "Certificate Management over CMS              (CMC)", RFC 5272, DOI 10.17487/RFC5272, June 2008,              <https://www.rfc-editor.org/info/rfc5272>.   [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>.   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",              RFC 7950, DOI 10.17487/RFC7950, August 2016,              <https://www.rfc-editor.org/info/rfc7950>.   [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>.   [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>.   [RFC8572]  Watsen, K., Farrer, I., and M. Abrahamsson, "Secure Zero              Touch Provisioning (SZTP)", RFC 8572,              DOI 10.17487/RFC8572, April 2019,              <https://www.rfc-editor.org/info/rfc8572>.   [RFC8791]  Bierman, A., Björklund, M., and K. Watsen, "YANG Data              Structure Extensions", RFC 8791, DOI 10.17487/RFC8791,              June 2020, <https://www.rfc-editor.org/info/rfc8791>.   [RFC9110]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,              Ed., "HTTP Semantics", STD 97, RFC 9110,              DOI 10.17487/RFC9110, June 2022,              <https://www.rfc-editor.org/info/rfc9110>.   [RFC9640]  Watsen, K., "YANG Data Types and Groupings for              Cryptography", RFC 9640, DOI 10.17487/RFC9640, October              2024, <https://www.rfc-editor.org/info/rfc9640>.6.2.  Informative References   [AIS31]    Killmann, W. and W. Schindler, "A proposal for:              Functionality classes for random number generators -              Version 2.0", September 2011,              <https://www.bsi.bund.de/SharedDocs/Downloads/DE/BSI/              Zertifizierung/Interpretationen/AIS_31_Functionality_class              es_for_random_number_generators_e.pdf>.   [CVE-2008-0166]              National Institute of Science and Technology (NIST),              "National Vulnerability Database - CVE-2008-0166 Detail",              May 2008,              <https://nvd.nist.gov/vuln/detail/CVE-2008-0166>.   [ISO.20543-2019]              International Organization for Standardization (ISO),              "Information technology -- Security techniques -- Test and              analysis methods for random bit generators within ISO/IEC              19790 and ISO/IEC 15408", ISO/IEC 20543:2019, October              2019.   [MiningPsQs]              Heninger, N., Durumeric, Z., Wustrow, E., and J.              Halderman, "Mining Your Ps and Qs: Detection of Widespread              Weak Keys in Network Devices", Security'12: Proceedings of              the 21st USENIX Conference on Security Symposium, August              2012, <https://www.usenix.org/conference/usenixsecurity12/              technical-sessions/presentation/heninger>.   [NIST.SP.800-90Ar1]              Barker, E. and J. Kelsey, "Recommendation for Random              Number Generation Using Deterministic Random Bit              Generators", DOI 10.6028/NIST.SP.800-90Ar1, NIST              SP 800-90Ar1, June 2015,              <https://nvlpubs.nist.gov/nistpubs/SpecialPublications/              NIST.SP.800-90Ar1.pdf>.   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,              "Randomness Requirements for Security", BCP 106, RFC 4086,              DOI 10.17487/RFC4086, June 2005,              <https://www.rfc-editor.org/info/rfc4086>.   [RFC7292]  Moriarty, K., Ed., Nystrom, M., Parkinson, S., Rusch, A.,              and M. Scott, "PKCS #12: Personal Information Exchange              Syntax v1.1", RFC 7292, DOI 10.17487/RFC7292, July 2014,              <https://www.rfc-editor.org/info/rfc7292>.   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,              <https://www.rfc-editor.org/info/rfc8340>.   [RFC8407]  Bierman, A., "Guidelines for Authors and Reviewers of              Documents Containing YANG Data Models", BCP 216, RFC 8407,              DOI 10.17487/RFC8407, October 2018,              <https://www.rfc-editor.org/info/rfc8407>.   [RFC8792]  Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,              "Handling Long Lines in Content of Internet-Drafts and              RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,              <https://www.rfc-editor.org/info/rfc8792>.   [RFC8808]  Wu, Q., Lengyel, B., and Y. Niu, "A YANG Data Model for              Factory Default Settings", RFC 8808, DOI 10.17487/RFC8808,              August 2020, <https://www.rfc-editor.org/info/rfc8808>.   [RFC9641]  Watsen, K., "A YANG Data Model for a Truststore",              RFC 9641, DOI 10.17487/RFC9641, October 2024,              <https://www.rfc-editor.org/info/rfc9641>.   [RFC9642]  Watsen, K., "A YANG Data Model for a Keystore", RFC 9642,              DOI 10.17487/RFC9642, October 2024,              <https://www.rfc-editor.org/info/rfc9642>.   [Std-802.1AR-2018]              IEEE, "IEEE Standard for Local and Metropolitan Area              Networks - Secure Device Identity", August 2018,              <https://standards.ieee.org/ieee/802.1AR/6995/>.Acknowledgements   The authors would like to thank for following for lively discussions   on list and in the halls (ordered by first name): Benjamin Kaduk, Dan   Romascanu, David von Oheimb, Éric Vyncke, Guy Fedorkow, Hendrik   Brockhaus, Joe Clarke, Meral Shirazipour, Murray Kucherawy, Rich   Salz, Rob Wilton, Roman Danyliw, Qin Wu, Yaron Sheffer, and   Zaheduzzaman Sarkar.Contributors   Special thanks go to David von Oheimb and Hendrik Brockhaus for   helping with the descriptions for the "cmc-csr" and "cmp-csr" nodes.Authors' Addresses   Kent Watsen   Watsen Networks   Email: kent+ietf@watsen.net   Russ Housley   Vigil Security, LLC   Email: housley@vigilsec.com   Sean Turner   sn3rd   Email: sean@sn3rd.com