A YANG Data Model for a Truststore

                               crypto-types
                                 ^      ^
                                /        \
                               /          \
                      truststore         keystore
                       ^     ^             ^  ^
                       |     +---------+   |  |
                       |               |   |  |
                       |      +------------+  |
tcp-client-server      |     /         |      |
   ^    ^        ssh-client-server     |      |
   |    |           ^            tls-client-server
   |    |           |              ^     ^        http-client-server
   |    |           |              |     |                 ^
   |    |           |        +-----+     +---------+       |
   |    |           |        |                     |       |
   |    +-----------|--------|--------------+      |       |
   |                |        |              |      |       |
   +-----------+    |        |              |      |       |
               |    |        |              |      |       |
               |    |        |              |      |       |
            netconf-client-server       restconf-client-server

module ietf-truststore {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-truststore";
  prefix ts;

  import ietf-netconf-acm {
    prefix nacm;
    reference
      "RFC 8341: Network Configuration Access Control Model";
  }

  import ietf-crypto-types {
    prefix ct;
    reference
      "RFC AAAA: 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>
     Author  : Kent Watsen <kent+ietf@watsen.net>";

  description
    "This module defines a 'truststore' to centralize management
     of trust anchors including certificates and public keys.

     Copyright (c) 2023 IETF Trust and the persons identified
     as authors of the code. All rights reserved.

     Redistribution and use in source and binary forms, with
     or without modification, is permitted pursuant to, and
     subject to the license terms contained in, the Revised
     BSD License set forth in Section 4.c of the IETF Trust's
     Legal Provisions Relating to IETF Documents
     (https://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC BBBB
     (https://www.rfc-editor.org/info/rfcBBBB); 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 2024-02-04 {
    description
      "Initial version";
    reference
      "RFC BBBB: A YANG Data Model for a Truststore";
  }

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

  feature central-truststore-supported {
    description
      "The 'central-truststore-supported' feature indicates that
       the server supports the truststore (i.e., implements the
       'ietf-truststore' module).";
  }

  feature inline-definitions-supported {
    description
      "The 'inline-definitions-supported' feature indicates that
       the server supports locally-defined trust anchors.";
  }

  feature certificates {
    description
      "The 'certificates' feature indicates that the server
       implements the /truststore/certificate-bags subtree.";
  }

  feature public-keys {
    description
      "The 'public-keys' feature indicates that the server
       implements the /truststore/public-key-bags subtree.";
  }

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

  typedef central-certificate-bag-ref {
    type leafref {
      path "/ts:truststore/ts:certificate-bags/"
         + "ts:certificate-bag/ts:name";
    }
    description
      "This typedef defines a reference to a certificate bag
       in the central truststore.";
  }

  typedef central-certificate-ref {
    type leafref {
      path "/ts:truststore/ts:certificate-bags/ts:certificate-bag"
         + "[ts:name = current()/../certificate-bag]/"
         + "ts:certificate/ts:name";
    }
    description
      "This typedef defines a reference to a specific certificate
       in a certificate bag in the central truststore. This typedef
       requires that there exist a sibling 'leaf' node called
       'certificate-bag' that SHOULD have the typedef
       'central-certificate-bag-ref'.";
  }

  typedef central-public-key-bag-ref {
    type leafref {
      path "/ts:truststore/ts:public-key-bags/"
         + "ts:public-key-bag/ts:name";
    }
    description
      "This typedef defines a reference to a public key bag
       in the central truststore.";
  }

  typedef central-public-key-ref {
    type leafref {
      path "/ts:truststore/ts:public-key-bags/ts:public-key-bag"
         + "[ts:name = current()/../public-key-bag]/"
         + "ts:public-key/ts:name";
    }
    description
      "This typedef defines a reference to a specific public key
       in a public key bag in the truststore.  This typedef
       requires that there exist a sibling 'leaf' node called
       'public-key-bag' that SHOULD have the typedef
       'central-public-key-bag-ref'.";
  }

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

  // *-ref groupings

  grouping central-certificate-ref-grouping {
    description
      "Grouping for the reference to a certificate in a
       certificate-bag in the central truststore.";
    leaf certificate-bag {
      nacm:default-deny-write;
      if-feature "central-truststore-supported";
      if-feature "certificates";
      type ts:central-certificate-bag-ref;
      must "../certificate";
      description
        "Reference to a certificate-bag in the truststore.";
    }
    leaf certificate {
      nacm:default-deny-write;
      if-feature "central-truststore-supported";
      if-feature "certificates";
      type ts:central-certificate-ref;
      must "../certificate-bag";
      description
        "Reference to a specific certificate in the
         referenced certificate-bag.";
    }
  }

  grouping central-public-key-ref-grouping {
    description
      "Grouping for the reference to a public key in a
       public-key-bag in the central truststore.";
    leaf public-key-bag {
      nacm:default-deny-write;
      if-feature "central-truststore-supported";
      if-feature "public-keys";
      type ts:central-public-key-bag-ref;
      description
        "Reference of a public key bag in the truststore including
         the certificate to authenticate the TLS client.";
    }
    leaf public-key {
      nacm:default-deny-write;
      if-feature "central-truststore-supported";
      if-feature "public-keys";
      type ts:central-public-key-ref;
      description
        "Reference to a specific public key in the
         referenced public-key-bag.";
    }
  }

  // inline-or-truststore-* groupings

  grouping inline-or-truststore-certs-grouping {
    description
      "A grouping for the configuration of a list of certificates.
       The list of certificate may be defined inline or as a
       reference to a certificate bag in the central truststore.

       Servers that wish to define alternate truststore locations
       MUST augment in custom 'case' statements enabling
       references to those alternate truststore locations.";
    choice inline-or-truststore {
      nacm:default-deny-write;
      mandatory true;
      description
        "A choice between an inlined definition and a definition
         that exists in the truststore.";
      case inline {
        if-feature "inline-definitions-supported";
        container inline-definition {
          description
            "A container for locally configured trust anchor
             certificates.";
          list certificate {
            key "name";
            min-elements 1;
            description
              "A trust anchor certificate or chain of certificates.";
            leaf name {
              type string;
              description
                "An arbitrary name for this certificate.";
            }
            uses ct:trust-anchor-cert-grouping {
              refine "cert-data" {
                mandatory true;
              }
            }
          }
        }
      }
      case central-truststore {
        if-feature "central-truststore-supported";
        if-feature "certificates";
        leaf central-truststore-reference {
          type ts:central-certificate-bag-ref;
          description
            "A reference to a certificate bag that exists in the
             central truststore.";
        }
      }
    }
  }

  grouping inline-or-truststore-public-keys-grouping {
    description
      "A grouping that allows the public keys to be either
       configured locally, within the using data model, or be a
       reference to a public key bag stored in the truststore.

       Servers that wish to define alternate truststore locations
       SHOULD augment in custom 'case' statements enabling
       references to those alternate truststore locations.";
    choice inline-or-truststore {
      nacm:default-deny-write;
      mandatory true;
      description
        "A choice between an inlined definition and a definition
         that exists in the truststore.";
      case inline {
        if-feature "inline-definitions-supported";
        container inline-definition {
          description
            "A container to hold local public key definitions.";
          list public-key {
            key "name";
            description
              "A public key definition.";
            leaf name {
              type string;
              description
                "An arbitrary name for this public key.";
            }
            uses ct:public-key-grouping;
          }
        }
      }
      case central-truststore {
        if-feature "central-truststore-supported";
        if-feature "public-keys";
        leaf central-truststore-reference {
          type ts:central-public-key-bag-ref;
          description
            "A reference to a bag of public keys that exists
             in the central truststore.";
        }
      }
    }
  }


  // the truststore grouping

  grouping truststore-grouping {
    description
      "A grouping definition that enables use in other contexts.
       Where used, implementations MUST augment new 'case'
       statements into the various inline-or-truststore 'choice'
       statements to supply leafrefs to the model-specific
       location(s).";
    container certificate-bags {
      nacm:default-deny-write;
      if-feature "certificates";
      description
        "A collection of certificate bags.";
      list certificate-bag {
        key "name";
        description
          "A bag of certificates.  Each bag of certificates SHOULD
           be for a specific purpose.  For instance, one bag could
           be used to authenticate a specific set of servers, while
           another could be used to authenticate a specific set of
           clients.";
        leaf name {
          type string;
          description
            "An arbitrary name for this bag of certificates.";
        }
        leaf description {
          type string;
          description
            "A description for this bag of certificates.  The
             intended purpose for the bag SHOULD be described.";
        }
        list certificate {
          key "name";
          description
            "A trust anchor certificate or chain of certificates.";
          leaf name {
            type string;
            description
              "An arbitrary name for this certificate.";
          }
          uses ct:trust-anchor-cert-grouping {
            refine "cert-data" {
              mandatory true;
            }
          }
        }
      }
    }
    container public-key-bags {
      nacm:default-deny-write;
      if-feature "public-keys";
      description
        "A collection of public key bags.";
      list public-key-bag {
        key "name";
        description
          "A bag of public keys.  Each bag of keys SHOULD be for
           a specific purpose.  For instance, one bag could be used
           authenticate a specific set of servers, while another
           could be used to authenticate a specific set of clients.";
        leaf name {
          type string;
          description
            "An arbitrary name for this bag of public keys.";
        }
        leaf description {
          type string;
          description
            "A description for this bag public keys.  The
             intended purpose for the bag MUST be described.";
        }
        list public-key {
          key "name";
          description
            "A public key.";
          leaf name {
            type string;
            description
              "An arbitrary name for this public key.";
          }
          uses ct:public-key-grouping;
        }
      }
    }
  }

  /*********************************/
  /*   Protocol accessible nodes   */
  /*********************************/

  container truststore {
    if-feature central-truststore-supported;
    nacm:default-deny-write;
    description
      "The truststore contains bags of certificates and
       public keys.";
    uses truststore-grouping;
  }
}