path: root/doc/rfc/rfc9645.txt

Internet Engineering Task Force (IETF)                         K. Watsen
Request for Comments: 9645                               Watsen Networks
Category: Standards Track                                   October 2024
ISSN: 2070-1721


             YANG Groupings for TLS Clients and TLS Servers

Abstract

   This document presents four YANG 1.1 modules -- three IETF modules
   and one supporting IANA module.

   The three IETF modules are "ietf-tls-common", "ietf-tls-client", and
   "ietf-tls-server".  The "ietf-tls-client" and "ietf-tls-server"
   modules are the primary productions of this work, supporting the
   configuration and monitoring of TLS clients and servers.

   The IANA module is "iana-tls-cipher-suite-algs".  This module defines
   YANG enumerations that provide support for an IANA-maintained
   algorithm registry.

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/rfc9645.

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.  Regarding the Three IETF Modules
     1.2.  Relation to Other RFCs
     1.3.  Specification Language
     1.4.  Adherence to the NMDA
     1.5.  Conventions
   2.  The "ietf-tls-common" Module
     2.1.  Data Model Overview
     2.2.  Example Usage
     2.3.  YANG Module
   3.  The "ietf-tls-client" Module
     3.1.  Data Model Overview
     3.2.  Example Usage
     3.3.  YANG Module
   4.  The "ietf-tls-server" Module
     4.1.  Data Model Overview
     4.2.  Example Usage
     4.3.  YANG Module
   5.  Security Considerations
     5.1.  Considerations for the "iana-tls-cipher-suite-algs" YANG
           Module
     5.2.  Considerations for the "ietf-tls-common" YANG Module
     5.3.  Considerations for the "ietf-tls-client" YANG Module
     5.4.  Considerations for the "ietf-tls-server" YANG Module
   6.  IANA Considerations
     6.1.  The IETF XML Registry
     6.2.  The YANG Module Names Registry
     6.3.  Considerations for the "iana-tls-cipher-suite-algs" YANG
           Module
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Appendix A.  Script to Generate IANA-Maintained YANG Modules
   Acknowledgements
   Contributors
   Author's Address

1.  Introduction

   This document presents four YANG 1.1 [RFC7950] modules -- three IETF
   modules and one IANA module.

   The three IETF modules are "ietf-tls-common" (Section 2), "ietf-tls-
   client" (Section 3), and "ietf-tls-server" (Section 4).  The "ietf-
   tls-client" and "ietf-tls-server" modules are the primary productions
   of this work, supporting the configuration and monitoring of TLS
   clients and servers.

   The groupings defined in this document are expected to be used in
   conjunction with the groupings defined in an underlying transport-
   level module, such as the groupings defined in [RFC9643].  The
   transport-level data model enables the configuration of transport-
   level values such as a remote address, a remote port, a local
   address, and a local port.

   The IANA module is "iana-tls-cipher-suite-algs".  This module defines
   YANG enumerations that provide support for an IANA-maintained
   algorithm registry.

   IANA used the script in Appendix A to generate the "iana-tls-cipher-
   suite-algs" YANG module.  This document does not publish the initial
   version of the module; it is published and maintained by IANA.

1.1.  Regarding the Three IETF Modules

   The three IETF modules define features and groupings to model
   "generic" TLS clients and TLS servers, where "generic" should be
   interpreted as "least common denominator" rather than "complete."
   Basic TLS protocol support is afforded by these modules, leaving
   configuration of advance features to augmentations made by consuming
   modules.

   It is intended that the YANG groupings will be used by applications
   needing to configure TLS client and server protocol stacks.  For
   instance, these groupings are used to help define the data model for
   HTTPS [RFC9110] and clients and servers based on the Network
   Configuration Protocol (NETCONF) over TLS [RFC7589] in
   [HTTP-CLIENT-SERVER] and [NETCONF-CLIENT-SERVER], respectively.

   The "ietf-tls-client" and "ietf-tls-server" YANG modules each define
   one grouping, which is focused on just TLS-specific configuration,
   and specifically avoid any transport-level configuration, such as
   what ports to listen on or connect to.  This affords applications the
   opportunity to define their own strategy for how the underlying TCP
   connection is established.  For instance, applications supporting
   NETCONF Call Home [RFC8071] could use the "tls-server-grouping"
   grouping for the TLS parts it provides, while adding data nodes for
   the TCP-level call-home configuration.

   Both TLS 1.2 and TLS 1.3 may be configured.  TLS 1.2 [RFC5246] is
   obsoleted by TLS 1.3 [RFC8446] but is still in common use, and hence
   its "feature" statement is marked "status deprecated".

1.2.  Relation to Other RFCs

   This document presents four YANG modules [RFC7950] that are part of a
   collection of RFCs that work together to ultimately support the
   configuration of both the clients and servers of the NETCONF
   [RFC6241] and RESTCONF [RFC8040] protocols.

   The dependency relationship between the primary YANG groupings
   defined in the various RFCs is presented in the diagram below.  In
   some cases, a document may define secondary groupings that introduce
   dependencies not illustrated in the diagram.  The labels in the
   diagram are shorthand names for the defining RFCs.  The citation
   references for the shorthand names are provided below the diagram.

   Please note that the arrows in the diagram point from referencer to
   referenced.  For example, the "crypto-types" RFC does not have any
   dependencies, whilst the "keystore" RFC depends on the "crypto-types"
   RFC.

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

   +========================+==========================+
   | Label in Diagram       | Originating RFC          |
   +========================+==========================+
   | crypto-types           | [RFC9640]                |
   +------------------------+--------------------------+
   | truststore             | [RFC9641]                |
   +------------------------+--------------------------+
   | keystore               | [RFC9642]                |
   +------------------------+--------------------------+
   | tcp-client-server      | [RFC9643]                |
   +------------------------+--------------------------+
   | ssh-client-server      | [RFC9644]                |
   +------------------------+--------------------------+
   | tls-client-server      | RFC 9645                 |
   +------------------------+--------------------------+
   | http-client-server     | [HTTP-CLIENT-SERVER]     |
   +------------------------+--------------------------+
   | netconf-client-server  | [NETCONF-CLIENT-SERVER]  |
   +------------------------+--------------------------+
   | restconf-client-server | [RESTCONF-CLIENT-SERVER] |
   +------------------------+--------------------------+

         Table 1: Labels in Diagram to RFC Mapping

1.3.  Specification 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.  Adherence to the NMDA

   This document is compliant with the Network Management Datastore
   Architecture (NMDA) [RFC8342].  For instance, as described in
   [RFC9641] and [RFC9642], trust anchors and keys installed during
   manufacturing are expected to appear in <operational> (Section 5.3 of
   [RFC8342]) and <system> [SYSTEM-CONFIG] if implemented.

1.5.  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 use the XML [W3C.REC-xml-20081126]
   encoding.  Other encodings, such as JSON [RFC8259], could
   alternatively be used.

   Various examples in this document contain long lines that may be
   folded, as described in [RFC8792].

2.  The "ietf-tls-common" Module

   The TLS common model presented in this section contains features and
   groupings common to both TLS clients and TLS servers.  The "hello-
   params-grouping" grouping can be used to configure the list of TLS
   algorithms permitted by the TLS client or TLS server.  The lists of
   algorithms are ordered such that, if multiple algorithms are
   permitted by the client, the algorithm that appears first in its list
   and that is also permitted by the server is used for the TLS
   transport layer connection.  The ability to restrict the algorithms
   allowed is provided in this grouping for TLS clients and TLS servers
   that are capable of doing so and that may serve to make TLS clients
   and TLS servers compliant with local security policies.  This model
   supports both TLS 1.2 [RFC5246] and TLS 1.3 [RFC8446].

   Thus, in order to support both TLS 1.2 and TLS 1.3, the cipher suites
   part of the "hello-params-grouping" grouping should include the
   following three parameters for configuring its permitted TLS
   algorithms: TLS Cipher Suites, TLS SignatureScheme, and TLS Supported
   Groups.

2.1.  Data Model Overview

   This section provides an overview of the "ietf-tls-common" module in
   terms of its features, identities, and groupings.

2.1.1.  Features

   The following diagram lists all the "feature" statements defined in
   the "ietf-tls-common" module:

   Features:
     +-- tls12
     +-- tls13
     +-- hello-params
     +-- asymmetric-key-pair-generation
     +-- supported-algorithms

   The diagram above uses syntax that is similar to but not defined in
   [RFC8340].

   Please refer to the YANG module for a description of each feature.

2.1.2.  Identities

   The following diagram illustrates the relationship amongst the
   "identity" statements defined in the "ietf-tls-common" module:

   Identities:
     +-- tls-version-base
        +-- tls12
        +-- tls13

   The diagram above uses syntax that is similar to but not defined in
   [RFC8340].

   Comments:

   *  The diagram shows that there are two base identities.
   *  One base identity is used to specify TLS versions.  This base
      identity is "abstract" in the object-oriented programming sense
      because it defines a "class" of things rather than a specific
      thing.
   *  These base identities are "abstract" in the object-oriented
      programming sense because they only define a "class" of things
      rather than a specific thing.

2.1.3.  Groupings

   The "ietf-tls-common" module defines the following "grouping"
   statement:

   *  hello-params-grouping

   This grouping is presented in the following subsection.

2.1.3.1.  The "hello-params-grouping" Grouping

   The following tree diagram [RFC8340] illustrates the "hello-params-
   grouping" grouping:

     grouping hello-params-grouping:
       +-- tls-versions
       |  +-- min?   identityref
       |  +-- max?   identityref
       +-- cipher-suites
          +-- cipher-suite*   tlscsa:tls-cipher-suite-algorithm

   Comments:

   *  This grouping is used by both the "tls-client-grouping" and the
      "tls-server-grouping" groupings defined in Sections 3.1.2.1 and
      4.1.2.1, respectively.

   *  This grouping enables client and server configurations to specify
      the TLS versions and cipher suites that are to be used when
      establishing TLS sessions.

   *  The "cipher-suites" list is "ordered-by user".

2.1.4.  Protocol-Accessible Nodes

   The following tree diagram [RFC8340] lists all the protocol-
   accessible nodes defined in the "ietf-tls-common" module, without
   expanding the "grouping" statements:

   module: ietf-tls-common
     +--ro supported-algorithms {algorithm-discovery}?
        +--ro supported-algorithm*   tlscsa:tls-cipher-suite-algorithm

     rpcs:
       +---x generate-asymmetric-key-pair
               {asymmetric-key-pair-generation}?
          +---w input
          |  +---w algorithm
          |  |       tlscsa:tls-cipher-suite-algorithm
          |  +---w num-bits?               uint16
          |  +---w private-key-encoding
          |     +---w (private-key-encoding)
          |        +--:(cleartext) {ct:cleartext-private-keys}?
          |        |  +---w cleartext?   empty
          |        +--:(encrypted) {ct:encrypted-private-keys}?
          |        |  +---w encrypted
          |        |     +---w ks:encrypted-by-grouping
          |        +--:(hidden) {ct:hidden-private-keys}?
          |           +---w hidden?      empty
          +--ro output
             +--ro (key-or-hidden)?
                +--:(key)
                |  +---u ct:asymmetric-key-pair-grouping
                +--:(hidden)
                   +--ro location?
                           instance-identifier

   Comments:

   *  Protocol-accessible nodes are nodes that are accessible when the
      module is "implemented", as described in Section 5.6.5 of
      [RFC7950].

   *  The protocol-accessible nodes for the "ietf-tls-common" module are
      limited to the "supported-algorithms" container, which is
      constrained by the "algorithm-discovery" feature, and the
      "generate-asymmetric-key-pair" RPC, which is constrained by the
      "asymmetric-key-pair-generation" feature.

   *  The "encrypted-by-grouping" grouping is discussed in
      Section 2.1.3.1 of [RFC9642].

   *  The "asymmetric-key-pair-grouping" grouping is discussed in
      Section 2.1.4.6 of [RFC9640].

2.2.  Example Usage

   The following example illustrates the "hello-params-grouping"
   grouping when populated with some data.

   <!-- The outermost element below doesn't exist in the data model. -->
   <!--  It simulates if the "grouping" were a "container" instead.  -->

   <hello-params
      xmlns="urn:ietf:params:xml:ns:yang:ietf-tls-common"
      xmlns:tlscmn="urn:ietf:params:xml:ns:yang:ietf-tls-common">
     <tls-versions>
       <min>tlscmn:tls12</min>
       <max>tlscmn:tls13</max>
     </tls-versions>
     <cipher-suites>
       <cipher-suite>TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA</cipher-suite>
       <cipher-suite>TLS_DHE_RSA_WITH_AES_128_CBC_SHA256</cipher-suite>
       <cipher-suite>TLS_RSA_WITH_3DES_EDE_CBC_SHA</cipher-suite>
     </cipher-suites>
   </hello-params>

   The following example illustrates operational state data indicating
   the TLS algorithms supported by the server.

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <supported-algorithms
     xmlns="urn:ietf:params:xml:ns:yang:ietf-tls-common">
     <supported-algorithm>TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA</support\
   ed-algorithm>
     <supported-algorithm>TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384</supp\
   orted-algorithm>
     <supported-algorithm>TLS_DHE_RSA_WITH_AES_128_CBC_SHA256</supporte\
   d-algorithm>
     <supported-algorithm>TLS_RSA_WITH_3DES_EDE_CBC_SHA</supported-algo\
   rithm>
     <supported-algorithm>TLS_ECDHE_PSK_WITH_AES_256_GCM_SHA384</suppor\
   ted-algorithm>
     <supported-algorithm>TLS_DHE_PSK_WITH_CHACHA20_POLY1305_SHA256</su\
   pported-algorithm>
     <supported-algorithm>TLS_ECCPWD_WITH_AES_256_GCM_SHA384</supported\
   -algorithm>
     <supported-algorithm>TLS_PSK_WITH_AES_256_CCM</supported-algorithm>
     <supported-algorithm>TLS_PSK_WITH_AES_256_CCM_8</supported-algorit\
   hm>
     <supported-algorithm>TLS_DHE_PSK_WITH_CAMELLIA_256_CBC_SHA384</sup\
   ported-algorithm>
     <supported-algorithm>TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384</support\
   ed-algorithm>
     <supported-algorithm>TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA</supported\
   -algorithm>
     <supported-algorithm>TLS_DH_DSS_WITH_AES_128_GCM_SHA256</supported\
   -algorithm>
   </supported-algorithms>

   The following example illustrates the "generate-asymmetric-key-pair"
   RPC.

   REQUEST

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <rpc message-id="101"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <generate-asymmetric-key-pair
       xmlns="urn:ietf:params:xml:ns:yang:ietf-tls-common">
       <algorithm>TLS_ECDHE_PSK_WITH_AES_128_GCM_SHA256</algorithm>
       <num-bits>521</num-bits>
       <private-key-encoding>
         <encrypted>
           <asymmetric-key-ref>hidden-asymmetric-key</asymmetric-key-re\
   f>
         </encrypted>
       </private-key-encoding>
     </generate-asymmetric-key-pair>
   </rpc>

   RESPONSE

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <rpc-reply message-id="101"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
     xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-crypto-types"
     xmlns:tlscmn="urn:ietf:params:xml:ns:yang:ietf-tls-common">
     <tlscmn:public-key-format>ct:subject-public-key-info-format</tlscm\
   n:public-key-format>
     <tlscmn:public-key>BASE64VALUE=</tlscmn:public-key>
     <tlscmn:private-key-format>ct:ec-private-key-format</tlscmn:privat\
   e-key-format>
     <tlscmn:cleartext-private-key>BASE64VALUE=</tlscmn:cleartext-priva\
   te-key>
   </rpc-reply>

2.3.  YANG Module

   This YANG module has normative references to [RFC5288], [RFC5289],
   [RFC8422], [RFC9640], [RFC9642], [FIPS180-4], and [FIPS186-5].

   This YANG module has informative references to [RFC5246] and
   [RFC8446].

   <CODE BEGINS> file "ietf-tls-common@2024-10-10.yang"
   module ietf-tls-common {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-tls-common";
     prefix tlscmn;

     import iana-tls-cipher-suite-algs {
       prefix tlscsa;
       reference
         "RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
     }

     import ietf-crypto-types {
       prefix ct;
       reference
         "RFC 9640: YANG Data Types and Groupings for Cryptography";
     }

     import ietf-keystore {
       prefix ks;
       reference
         "RFC 9642: A YANG Data Model for a Keystore";
     }

     organization
       "IETF NETCONF (Network Configuration) Working Group";

     contact
       "WG List:  NETCONF WG list <mailto:netconf@ietf.org>
        WG Web:   https://datatracker.ietf.org/wg/netconf
        Author:   Kent Watsen <mailto:kent+ietf@watsen.net>
        Author:   Jeff Hartley <mailto:intensifysecurity@gmail.com>
        Author:   Gary Wu <mailto:garywu@cisco.com>";

      description
       "This module defines common features and groupings for
        Transport Layer Security (TLS).

        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 9645
        (https://www.rfc-editor.org/info/rfc9645); see the RFC
        itself for full legal notices.";

     revision 2024-10-10 {
       description
         "Initial version.";
       reference
         "RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
     }

     // Features

     feature tls12 {
       description
         "TLS Protocol Version 1.2 is supported. TLS 1.2 is obsolete,
          and thus it is NOT RECOMMENDED to enable this feature.";
       reference
         "RFC 5246: The Transport Layer Security (TLS) Protocol
                    Version 1.2";
     }

     feature tls13 {
       description
         "TLS Protocol Version 1.3 is supported.";
       reference
         "RFC 8446: The Transport Layer Security (TLS)
                    Protocol Version 1.3";
     }

     feature hello-params {
       description
         "TLS hello message parameters are configurable.";
     }

     feature algorithm-discovery {
       description
         "Indicates that the server implements the
          'supported-algorithms' container.";
     }

     feature asymmetric-key-pair-generation {
       description
         "Indicates that the server implements the
          'generate-asymmetric-key-pair' RPC.";
     }

     // Identities

     identity tls-version-base {
       description
         "Base identity used to identify TLS protocol versions.";
     }

     identity tls12 {
       if-feature "tls12";
       base tls-version-base;
       description
         "TLS Protocol Version 1.2.";
       reference
         "RFC 5246: The Transport Layer Security (TLS) Protocol
                    Version 1.2";
     }

     identity tls13 {
       if-feature "tls13";
       base tls-version-base;
       description
         "TLS Protocol Version 1.3.";
       reference
         "RFC 8446: The Transport Layer Security (TLS)
                    Protocol Version 1.3";
     }

     // Typedefs

     typedef epsk-supported-hash {
       type enumeration {
         enum sha-256 {
           description
             "The SHA-256 hash.";
         }
         enum sha-384 {
           description
             "The SHA-384 hash.";
         }
       }
       description
         "As per Section 4.2.11 of RFC 8446, the hash algorithm
          supported by an instance of an External Pre-Shared
          Key (EPSK).";
       reference
         "RFC 8446: The Transport Layer Security (TLS)
                    Protocol Version 1.3";
     }


     // Groupings

     grouping hello-params-grouping {
       description
         "A reusable grouping for TLS hello message parameters.";
       reference
         "RFC 5246: The Transport Layer Security (TLS) Protocol
                    Version 1.2
          RFC 8446: The Transport Layer Security (TLS) Protocol
                    Version 1.3";
       container tls-versions {
         description
           "Parameters limiting which TLS versions, amongst
            those enabled by 'features', are presented during
            the TLS handshake.";
         leaf min {
           type identityref {
             base tls-version-base;
           }
           description
             "If not specified, then there is no configured
              minimum version.";
         }
         leaf max {
           type identityref {
             base tls-version-base;
           }
           description
             "If not specified, then there is no configured
              maximum version.";
         }
       }
       container cipher-suites {
         description
           "Parameters regarding cipher suites.";
         leaf-list cipher-suite {
           type tlscsa:tls-cipher-suite-algorithm;
           ordered-by user;
           description
             "Acceptable cipher suites in order of descending
              preference.  The configured host key algorithms should
              be compatible with the algorithm used by the configured
              private key.  Please see Section 5 of RFC 9645 for
              valid combinations.

              If this leaf-list is not configured (has zero elements),
              the acceptable cipher suites are implementation-
              defined.";
           reference
             "RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
         }
       }
     } // hello-params-grouping


     // Protocol-accessible Nodes

     container supported-algorithms {
       if-feature "algorithm-discovery";
       config false;
       description
         "A container for a list of cipher suite algorithms supported
          by the server.";
       leaf-list supported-algorithm {
         type tlscsa:tls-cipher-suite-algorithm;
         description
           "A cipher suite algorithm supported by the server.";
       }
     }

     rpc generate-asymmetric-key-pair {
       if-feature "asymmetric-key-pair-generation";
       description
         "Requests the device to generate an 'asymmetric-key-pair'
          key using the specified key algorithm.";
       input {
         leaf algorithm {
           type tlscsa:tls-cipher-suite-algorithm;
           mandatory true;
           description
             "The cipher suite algorithm that the generated key
              works with.  Implementations derive the public key
              algorithm from the cipher suite algorithm.  For
              example, cipher suite
              'tls-rsa-with-aes-256-cbc-sha256' maps to the RSA
              public key.";
         }
         leaf num-bits {
           type uint16;
           description
             "Specifies the number of bits to create in the key.
              For RSA keys, the minimum size is 1024 bits, and
              the default is 3072 bits.  Generally, 3072 bits is
              considered sufficient.  DSA keys must be exactly
              1024 bits as specified by FIPS 186-2.  For
              elliptical keys, the 'num-bits' value determines
              the key length of the curve (e.g., 256, 384, or 521),
              where valid values supported by the server are
              conveyed via an unspecified mechanism.  For some
              public algorithms, the keys have a fixed length, and
              thus the 'num-bits' value is not specified.";
         }
         container private-key-encoding {
           description
             "Indicates how the private key is to be encoded.";
           choice private-key-encoding {
             mandatory true;
             description
               "A choice amongst optional private key handling.";
             case cleartext {
               if-feature "ct:cleartext-private-keys";
               leaf cleartext {
                 type empty;
                 description
                   "Indicates that the private key is to be returned
                    as a cleartext value.";
               }
             }
             case encrypted {
               if-feature "ct:encrypted-private-keys";
               container encrypted {
                 description
                   "Indicates that the key is to be encrypted using
                    the specified symmetric or asymmetric key.";
                 uses ks:encrypted-by-grouping;
               }
             }
             case hidden {
               if-feature "ct:hidden-private-keys";
               leaf hidden {
                 type empty;
                 description
                   "Indicates that the private key is to be hidden.

                    Unlike the 'cleartext' and 'encrypt' options, the
                    key returned is a placeholder for an internally
                    stored key.  See Section 3 of RFC 9642 ('Support
                    for Built-In Keys') for information about hidden
                    keys.";
               }
             }
           }
         }
       }
       output {
         choice key-or-hidden {
           case key {
             uses ct:asymmetric-key-pair-grouping;
           }
           case hidden {
             leaf location {
               type instance-identifier;
               description
                 "The location to where a hidden key was created.";
             }
           }
           description
             "The output can be either a key (for cleartext and
              encrypted keys) or the location to where the key
              was created (for hidden keys).";
         }
       }
     } // end generate-asymmetric-key-pair

   }
   <CODE ENDS>

3.  The "ietf-tls-client" Module

   This section defines a YANG 1.1 [RFC7950] module called "ietf-tls-
   client".  A high-level overview of the module is provided in
   Section 3.1.  Examples illustrating the module's use are provided in
   Section 3.2 ("Example Usage").  The YANG module itself is defined in
   Section 3.3.

3.1.  Data Model Overview

   This section provides an overview of the "ietf-tls-client" module in
   terms of its features and groupings.

3.1.1.  Features

   The following diagram lists all the "feature" statements defined in
   the "ietf-tls-client" module:

   Features:
     +-- tls-client-keepalives
     +-- client-ident-x509-cert
     +-- client-ident-raw-public-key
     +-- client-ident-psk
     +-- server-auth-x509-cert
     +-- server-auth-raw-public-key
     +-- server-auth-psk

   The diagram above uses syntax that is similar to but not defined in
   [RFC8340].

   Please refer to the YANG module for a description of each feature.

3.1.2.  Groupings

   The "ietf-tls-client" module defines the following "grouping"
   statement:

   *  tls-client-grouping

   This grouping is presented in the following subsection.

3.1.2.1.  The "tls-client-grouping" Grouping

   The following tree diagram [RFC8340] illustrates the "tls-client-
   grouping" grouping:

   =============== NOTE: '\' line wrapping per RFC 8792 ================

     grouping tls-client-grouping:
       +-- client-identity!
       |  +-- (auth-type)
       |     +--:(certificate) {client-ident-x509-cert}?
       |     |  +-- certificate
       |     |     +---u ks:inline-or-keystore-end-entity-cert-with-key\
   -grouping
       |     +--:(raw-public-key) {client-ident-raw-public-key}?
       |     |  +-- raw-private-key
       |     |     +---u ks:inline-or-keystore-asymmetric-key-grouping
       |     +--:(tls12-psk) {client-ident-tls12-psk}?
       |     |  +-- tls12-psk
       |     |     +---u ks:inline-or-keystore-symmetric-key-grouping
       |     |     +-- id?
       |     |             string
       |     +--:(tls13-epsk) {client-ident-tls13-epsk}?
       |        +-- tls13-epsk
       |           +---u ks:inline-or-keystore-symmetric-key-grouping
       |           +-- external-identity
       |           |       string
       |           +-- hash?
       |           |       tlscmn:epsk-supported-hash
       |           +-- context?
       |           |       string
       |           +-- target-protocol?
       |           |       uint16
       |           +-- target-kdf?
       |                   uint16
       +-- server-authentication
       |  +-- ca-certs! {server-auth-x509-cert}?
       |  |  +---u ts:inline-or-truststore-certs-grouping
       |  +-- ee-certs! {server-auth-x509-cert}?
       |  |  +---u ts:inline-or-truststore-certs-grouping
       |  +-- raw-public-keys! {server-auth-raw-public-key}?
       |  |  +---u ts:inline-or-truststore-public-keys-grouping
       |  +-- tls12-psks?        empty {server-auth-tls12-psk}?
       |  +-- tls13-epsks?       empty {server-auth-tls13-epsk}?
       +-- hello-params {tlscmn:hello-params}?
       |  +---u tlscmn:hello-params-grouping
       +-- keepalives {tls-client-keepalives}?
          +-- peer-allowed-to-send?   empty
          +-- test-peer-aliveness!
             +-- max-wait?       uint16
             +-- max-attempts?   uint8

   Comments:

   *  The "client-identity" node, which is optionally configured (as
      client authentication MAY occur at a higher protocol layer),
      configures identity credentials, each enabled by a "feature"
      statement defined in Section 3.1.1.

   *  The "server-authentication" node configures trust anchors for
      authenticating the TLS server, with each option enabled by a
      "feature" statement.

   *  The "hello-params" node, which must be enabled by a feature,
      configures parameters for the TLS sessions established by this
      configuration.

   *  The "keepalives" node, which must be enabled by a feature,
      configures a "presence" container to test the aliveness of the TLS
      server.  The aliveness-test occurs at the TLS protocol layer.

   *  For the referenced grouping statement(s):

      -  The "inline-or-keystore-end-entity-cert-with-key-grouping"
         grouping is discussed in Section 2.1.3.6 of [RFC9642].
      -  The "inline-or-keystore-asymmetric-key-grouping" grouping is
         discussed in Section 2.1.3.4 of [RFC9642].
      -  The "inline-or-keystore-symmetric-key-grouping" grouping is
         discussed in Section 2.1.3.3 of [RFC9642].
      -  The "inline-or-truststore-certs-grouping" grouping is discussed
         in Section 2.1.3.3 of [RFC9641].
      -  The "inline-or-truststore-public-keys-grouping" grouping is
         discussed in Section 2.1.3.4 of [RFC9641].
      -  The "hello-params-grouping" grouping is discussed in
         Section 2.1.3.1 in this document.

3.1.3.  Protocol-Accessible Nodes

   The "ietf-tls-client" module defines only "grouping" statements that
   are used by other modules to instantiate protocol-accessible nodes.
   Thus, this module does not itself define any protocol-accessible
   nodes when implemented.

3.2.  Example Usage

   This section presents two examples showing the "tls-client-grouping"
   grouping populated with some data.  These examples are effectively
   the same except the first configures the client identity using a
   local key while the second uses a key configured in a keystore.  Both
   examples are consistent with the examples presented in Section 2.2.1
   of [RFC9641] and Section 2.2.1 of [RFC9642].

   The following configuration example uses inline-definitions for the
   client identity and server authentication:

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <!-- The outermost element below doesn't exist in the data model. -->
   <!--  It simulates if the "grouping" were a "container" instead.  -->

   <tls-client
     xmlns="urn:ietf:params:xml:ns:yang:ietf-tls-client"
     xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-crypto-types">

       <!-- how this client will authenticate itself to the server  -->
       <client-identity>
           <certificate>
               <inline-definition>
                   <private-key-format>ct:rsa-private-key-format</priva\
   te-key-format>
                   <cleartext-private-key>BASE64VALUE=</cleartext-priva\
   te-key>
                   <cert-data>BASE64VALUE=</cert-data>
               </inline-definition>
           </certificate>
       </client-identity>

       <!-- which certificates will this client trust -->
       <server-authentication>
           <ca-certs>
               <inline-definition>
                   <certificate>
                       <name>Server Cert Issuer #1</name>
                       <cert-data>BASE64VALUE=</cert-data>
                   </certificate>
                   <certificate>
                       <name>Server Cert Issuer #2</name>
                       <cert-data>BASE64VALUE=</cert-data>
                   </certificate>
               </inline-definition>
           </ca-certs>
           <ee-certs>
               <inline-definition>
                   <certificate>
                       <name>My Application #1</name>
                       <cert-data>BASE64VALUE=</cert-data>
                   </certificate>
                   <certificate>
                       <name>My Application #2</name>
                       <cert-data>BASE64VALUE=</cert-data>
                   </certificate>
               </inline-definition>
           </ee-certs>
           <raw-public-keys>
               <inline-definition>
                   <public-key>
                       <name>corp-fw1</name>
                       <public-key-format>ct:subject-public-key-info-fo\
   rmat</public-key-format>
                       <public-key>BASE64VALUE=</public-key>
                   </public-key>
                   <public-key>
                       <name>corp-fw2</name>
                       <public-key-format>ct:subject-public-key-info-fo\
   rmat</public-key-format>
                       <public-key>BASE64VALUE=</public-key>
                   </public-key>
               </inline-definition>
           </raw-public-keys>
           <tls12-psks/>
           <tls13-epsks/>
       </server-authentication>

       <keepalives>
           <test-peer-aliveness>
               <max-wait>30</max-wait>
               <max-attempts>3</max-attempts>
           </test-peer-aliveness>
       </keepalives>

   </tls-client>

   The following configuration example uses central-keystore-references
   for the client identity and central-truststore-references for server
   authentication from the keystore:

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <!-- The outermost element below doesn't exist in the data model. -->
   <!--  It simulates if the "grouping" were a "container" instead.  -->

   <tls-client xmlns="urn:ietf:params:xml:ns:yang:ietf-tls-client">

       <!-- how this client will authenticate itself to the server -->
       <client-identity>
           <certificate>
               <central-keystore-reference>
                   <asymmetric-key>rsa-asymmetric-key</asymmetric-key>
                   <certificate>ex-rsa-cert</certificate>
               </central-keystore-reference>
           </certificate>
       </client-identity>

       <!-- which certificates will this client trust -->
       <server-authentication>
           <ca-certs>
               <central-truststore-reference>trusted-server-ca-certs</c\
   entral-truststore-reference>
           </ca-certs>
           <ee-certs>
               <central-truststore-reference>trusted-server-ee-certs</c\
   entral-truststore-reference>
           </ee-certs>
           <raw-public-keys>
               <central-truststore-reference>Raw Public Keys for TLS Se\
   rvers</central-truststore-reference>
           </raw-public-keys>
           <tls12-psks/>
           <tls13-epsks/>
       </server-authentication>

       <keepalives>
           <test-peer-aliveness>
               <max-wait>30</max-wait>
               <max-attempts>3</max-attempts>
           </test-peer-aliveness>
       </keepalives>

   </tls-client>

3.3.  YANG Module

   This YANG module has normative references to [RFC4279], [RFC5280],
   [RFC6520], [RFC7250], [RFC9640], [RFC9641], and [RFC9642] and
   informative references to [RFC5056], [RFC5246], [RFC8446], [RFC9258],
   and [RFC9257].

   <CODE BEGINS> file "ietf-tls-client@2024-10-10.yang"
   module ietf-tls-client {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-tls-client";
     prefix tlsc;

     import ietf-netconf-acm {
       prefix nacm;
       reference
         "RFC 8341: Network Configuration Access Control Model";
     }
     import ietf-crypto-types {
       prefix ct;
       reference
         "RFC 9640: YANG Data Types and Groupings for Cryptography";
     }
     import ietf-truststore {
       prefix ts;
       reference
         "RFC 9641: A YANG Data Model for a Truststore";
     }
     import ietf-keystore {
       prefix ks;
       reference
         "RFC 9642: A YANG Data Model for a Keystore";
     }
     import ietf-tls-common {
       prefix tlscmn;
       reference
         "RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
     }

     organization
       "IETF NETCONF (Network Configuration) Working Group";
     contact
       "WG List:  NETCONF WG list <mailto:netconf@ietf.org>
        WG Web:   https://datatracker.ietf.org/wg/netconf
        Author:   Kent Watsen <mailto:kent+ietf@watsen.net>
        Author:   Jeff Hartley <mailto:intensifysecurity@gmail.com>";
     description
       "This module defines reusable groupings for TLS clients that
        can be used as a basis for specific TLS client instances.

        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 9645
        (https://www.rfc-editor.org/info/rfc9645); see the RFC
        itself for full legal notices.";

     revision 2024-10-10 {
       description
         "Initial version";
       reference
         "RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
     }

     // Features

     feature tls-client-keepalives {
       description
         "Per-socket TLS keepalive parameters are configurable for
          TLS clients on the server implementing this feature.";
     }

     feature client-ident-x509-cert {
       description
         "Indicates that the client supports identifying itself
          using X.509 certificates.";
       reference
         "RFC 5280:
            Internet X.509 Public Key Infrastructure Certificate
            and Certificate Revocation List (CRL) Profile";
     }

     feature client-ident-raw-public-key {
       description
         "Indicates that the client supports identifying itself
          using raw public keys.";
       reference
         "RFC 7250:
            Using Raw Public Keys in Transport Layer Security (TLS)
            and Datagram Transport Layer Security (DTLS)";
     }

     feature client-ident-tls12-psk {
       if-feature "tlscmn:tls12";
       description
         "Indicates that the client supports identifying itself
          using TLS 1.2 PSKs (pre-shared or pairwise symmetric keys).";
       reference
         "RFC 4279:
            Pre-Shared Key Ciphersuites for Transport Layer Security
            (TLS)";
     }

     feature client-ident-tls13-epsk {
       if-feature "tlscmn:tls13";
       description
         "Indicates that the client supports identifying itself
          using TLS 1.3 External PSKs (pre-shared keys).";
       reference
         "RFC 8446:
            The Transport Layer Security (TLS) Protocol Version 1.3";
     }

     feature server-auth-x509-cert {
       description
         "Indicates that the client supports authenticating servers
          using X.509 certificates.";
       reference
         "RFC 5280:
            Internet X.509 Public Key Infrastructure Certificate
            and Certificate Revocation List (CRL) Profile";
     }

     feature server-auth-raw-public-key {
       description
         "Indicates that the client supports authenticating servers
          using raw public keys.";
       reference
         "RFC 7250:
            Using Raw Public Keys in Transport Layer Security (TLS)
            and Datagram Transport Layer Security (DTLS)";
     }

     feature server-auth-tls12-psk {
       description
         "Indicates that the client supports authenticating servers
          using PSKs (pre-shared or pairwise symmetric keys).";
       reference
         "RFC 4279:
            Pre-Shared Key Ciphersuites for Transport Layer Security
            (TLS)";
     }

     feature server-auth-tls13-epsk {
       description
         "Indicates that the client supports authenticating servers
          using TLS 1.3 External PSKs (pre-shared keys).";
       reference
         "RFC 8446:
            The Transport Layer Security (TLS) Protocol Version 1.3";
     }

     // Groupings

     grouping tls-client-grouping {
       description
         "A reusable grouping for configuring a TLS client without
          any consideration for how an underlying TCP session is
          established.

          Note that this grouping uses fairly typical descendant
          node names such that a stack of 'uses' statements will
          have name conflicts.  It is intended that the consuming
          data model will resolve the issue (e.g., by wrapping
          the 'uses' statement in a container called
          'tls-client-parameters').  This model purposely does
          not do this itself so as to provide maximum flexibility
          to consuming models.";
       container client-identity {
         nacm:default-deny-write;
         presence "Indicates that a TLS-level client identity has been
                   configured.  This statement is present so the
                   mandatory descendant nodes do not imply that this
                   node must be configured.";
         description
           "Identity credentials the TLS client MAY present when
            establishing a connection to a TLS server.  If not
            configured, then client authentication is presumed to
            occur in a protocol layer above TLS.  When configured,
            and requested by the TLS server when establishing a
            TLS session, these credentials are passed in the
            Certificate message defined in Section 7.4.2 of
            RFC 5246 and Section 4.4.2 of RFC 8446.";
         reference
           "RFC 5246: The Transport Layer Security (TLS)
                      Protocol Version 1.2
            RFC 8446: The Transport Layer Security (TLS)
                      Protocol Version 1.3
            RFC 9642: A YANG Data Model for a Keystore";
         choice auth-type {
           mandatory true;
           description
             "A choice amongst authentication types, of which one must
              be enabled (via its associated 'feature') and selected.";
           case certificate {
             if-feature "client-ident-x509-cert";
             container certificate {
               description
                 "Specifies the client identity using a certificate.";
               uses "ks:inline-or-keystore-end-entity-cert-with-key-"
                  + "grouping" {
                 refine "inline-or-keystore/inline/inline-definition" {
                   must 'not(public-key-format) or derived-from-or-self'
                      + '(public-key-format, "ct:subject-public-key-'
                      + 'info-format")';
                 }
                 refine "inline-or-keystore/central-keystore/"
                      + "central-keystore-reference/asymmetric-key" {
                   must 'not(deref(.)/../ks:public-key-format) or '
                      + 'derived-from-or-self(deref(.)/../ks:public-'
                      + 'key-format, "ct:subject-public-key-info-'
                      + 'format")';
                 }
               }
             }
           }
           case raw-public-key {
             if-feature "client-ident-raw-public-key";
             container raw-private-key {
               description
                 "Specifies the client identity using a raw
                  private key.";
               uses ks:inline-or-keystore-asymmetric-key-grouping {
                 refine "inline-or-keystore/inline/inline-definition" {
                   must 'not(public-key-format) or derived-from-or-self'
                      + '(public-key-format, "ct:subject-public-key-'
                      + 'info-format")';
                 }
                 refine "inline-or-keystore/central-keystore/"
                      + "central-keystore-reference" {
                   must 'not(deref(.)/../ks:public-key-format) or '
                      + 'derived-from-or-self(deref(.)/../ks:public-'
                      + 'key-format, "ct:subject-public-key-info-'
                      + 'format")';
                 }
               }
             }
           }
           case tls12-psk {
             if-feature "client-ident-tls12-psk";
             container tls12-psk {
               description
                 "Specifies the client identity using a PSK (pre-shared
                  or pairwise symmetric key).";
               uses ks:inline-or-keystore-symmetric-key-grouping;
               leaf id {
                 type string;
                 description
                   "The key 'psk_identity' value used in the TLS
                    'ClientKeyExchange' message.";
                 reference
                   "RFC 4279: Pre-Shared Key Ciphersuites for
                              Transport Layer Security (TLS)";
               }
             }
           }
           case tls13-epsk {
             if-feature "client-ident-tls13-epsk";
             container tls13-epsk {
               description
                 "An External Pre-Shared Key (EPSK) is established
                  or provisioned out of band, i.e., not from a TLS
                  connection.  An EPSK is a tuple of (Base Key,
                  External Identity, Hash).  EPSKs MUST NOT be
                  imported for (D)TLS 1.2 or prior versions.  When
                  PSKs are provisioned out of band, the PSK identity
                  and the Key Derivation Function (KDF) hash algorithm
                  to be used with the PSK MUST also be provisioned.

                  The structure of this container is designed to satisfy
                  the requirements in Section 4.2.11 of RFC 8446, the
                  recommendations from Section 6 of RFC 9257, and the
                  EPSK input fields detailed in Section 5.1 of RFC 9258.
                  The base-key is based upon
                  'ks:inline-or-keystore-symmetric-key-grouping' in
                  order to provide users with flexible and secure
                  storage options.";
               reference
                 "RFC 8446: The Transport Layer Security (TLS)
                            Protocol Version 1.3
                  RFC 9257: Guidance for External Pre-Shared Key
                            (PSK) Usage in TLS
                  RFC 9258: Importing External Pre-Shared Keys
                            (PSKs) for TLS 1.3";
               uses ks:inline-or-keystore-symmetric-key-grouping;
               leaf external-identity {
                 type string;
                 mandatory true;
                 description
                   "As per Section 4.2.11 of RFC 8446 and Section 4.1
                    of RFC 9257, a sequence of bytes used to identify
                    an EPSK.  A label for a pre-shared key established
                    externally.";
                 reference
                   "RFC 8446: The Transport Layer Security (TLS)
                              Protocol Version 1.3
                    RFC 9257: Guidance for External Pre-Shared Key
                              (PSK) Usage in TLS";
               }
               leaf hash {
                 type tlscmn:epsk-supported-hash;
                 default "sha-256";
                 description
                   "As per Section 4.2.11 of RFC 8446, for EPSKs,
                    the hash algorithm MUST be set when the PSK is
                    established; otherwise, default to SHA-256 if
                    no such algorithm is defined.  The server MUST
                    ensure that it selects a compatible PSK (if any)
                    and cipher suite.  Each PSK MUST only be used
                    with a single hash function.";
                 reference
                   "RFC 8446: The Transport Layer Security (TLS)
                              Protocol Version 1.3";
               }
               leaf context {
                 type string;
                 description
                   "As per Section 5.1 of RFC 9258, context MUST
                    include the context used to determine the EPSK,
                    if any exists.  For example, context may include
                    information about peer roles or identities
                    to mitigate Selfie-style reflection attacks.
                    Since the EPSK is a key derived from an external
                    protocol or a sequence of protocols, context MUST
                    include a channel binding for the deriving
                    protocols (see RFC 5056).  The details of this
                    binding are protocol specific and out of scope
                    for this document.";
                 reference
                   "RFC 9258: Importing External Pre-Shared Keys
                              (PSKs) for TLS 1.3";
               }
               leaf target-protocol {
                 type uint16;
                 description
                   "As per Section 3 of RFC 9258, the protocol
                    for which a PSK is imported for use.";
                 reference
                   "RFC 9258: Importing External Pre-Shared Keys
                              (PSKs) for TLS 1.3";
               }
               leaf target-kdf {
                 type uint16;
                 description
                   "As per Section 3 of RFC 9258, the Key Derivation
                    Function (KDF) for which a PSK is imported for
                    use.";
                 reference
                   "RFC 9258: Importing External Pre-Shared Keys
                              (PSKs) for TLS 1.3";
               }
             }
           }
         }
       } // container client-identity
       container server-authentication {
         nacm:default-deny-write;
         must "ca-certs or ee-certs or raw-public-keys or tls12-psks
                       or tls13-epsks";
         description
           "Specifies how the TLS client can authenticate TLS servers.
            Any combination of credentials is additive and unordered.

            Note that no configuration is required for authentication
            based on PSK (pre-shared or pairwise symmetric key) as
            the key is necessarily the same as configured in the
            '../client-identity' node.";
         container ca-certs {
           if-feature "server-auth-x509-cert";
           presence "Indicates that Certification Authority (CA)
                     certificates have been configured.  This
                     statement is present so the mandatory
                     descendant nodes do not imply that this
                     node must be configured.";
           description
             "A set of CA certificates used by the TLS client to
              authenticate TLS server certificates.  A server
              certificate is authenticated if it has a valid chain of
              trust to a configured CA certificate.";
           reference
             "RFC 9641: A YANG Data Model for a Truststore";
           uses ts:inline-or-truststore-certs-grouping;
         }
         container ee-certs {
           if-feature "server-auth-x509-cert";
           presence "Indicates that End-Entity (EE) certificates have
                     been configured.  This statement is present so
                     the mandatory descendant nodes do not imply
                     that this node must be configured.";
           description
             "A set of server certificates (i.e., EE certificates) used
              by the TLS client to authenticate certificates presented
              by TLS servers.  A server certificate is authenticated if
              it is an exact match to a configured server certificate.";
           reference
             "RFC 9641: A YANG Data Model for a Truststore";
           uses ts:inline-or-truststore-certs-grouping;
         }
         container raw-public-keys {
           if-feature "server-auth-raw-public-key";
           presence "Indicates that raw public keys have been
                     configured.  This statement is present so
                     the mandatory descendant nodes do not imply
                     that this node must be configured.";
           description
             "A set of raw public keys used by the TLS client to
              authenticate raw public keys presented by the TLS
              server.  A raw public key is authenticated if it
              is an exact match to a configured raw public key.";
           reference
             "RFC 9641: A YANG Data Model for a Truststore";
           uses ts:inline-or-truststore-public-keys-grouping {
             refine "inline-or-truststore/inline/inline-definition/"
                  + "public-key" {
               must 'derived-from-or-self(public-key-format,'
                  + ' "ct:subject-public-key-info-format")';
             }
             refine "inline-or-truststore/central-truststore/"
                  + "central-truststore-reference" {
               must 'not(deref(.)/../ts:public-key/ts:public-key-'
                  + 'format[not(derived-from-or-self(., "ct:subject-'
                  + 'public-key-info-format"))])';
             }
           }
         }
         leaf tls12-psks {
           if-feature "server-auth-tls12-psk";
           type empty;
           description
             "Indicates that the TLS client can authenticate TLS servers
              using configured PSKs (pre-shared or pairwise symmetric
              keys).

              No configuration is required since the PSK value is the
              same as the PSK value configured in the 'client-identity'
              node.";
         }
         leaf tls13-epsks {
           if-feature "server-auth-tls13-epsk";
           type empty;
           description
             "Indicates that the TLS client can authenticate TLS servers
              using configured External PSKs (pre-shared keys).

              No configuration is required since the PSK value is the
              same as the PSK value configured in the 'client-identity'
              node.";
         }
       } // container server-authentication
       container hello-params {
         nacm:default-deny-write;
         if-feature "tlscmn:hello-params";
         uses tlscmn:hello-params-grouping;
         description
           "Configurable parameters for the TLS hello message.";
       } // container hello-params
       container keepalives {
         nacm:default-deny-write;
         if-feature "tls-client-keepalives";
         description
           "Configures the keepalive policy for the TLS client.";
         leaf peer-allowed-to-send {
           type empty;
           description
             "Indicates that the remote TLS server is allowed to send
              HeartbeatRequest messages, as defined by RFC 6520,
              to this TLS client.";
           reference
             "RFC 6520: Transport Layer Security (TLS) and Datagram
              Transport Layer Security (DTLS) Heartbeat Extension";
         }
         container test-peer-aliveness {
           presence "Indicates that the TLS client proactively tests the
                     aliveness of the remote TLS server.";
           description
             "Configures the keepalive policy to proactively test
              the aliveness of the TLS server.  An unresponsive
              TLS server is dropped after approximately max-wait
              * max-attempts seconds.  The TLS client MUST send
              HeartbeatRequest messages, as defined in RFC 6520.";
           reference
             "RFC 6520: Transport Layer Security (TLS) and Datagram
              Transport Layer Security (DTLS) Heartbeat Extension";
           leaf max-wait {
             type uint16 {
               range "1..max";
             }
             units "seconds";
             default "30";
             description
               "Sets the amount of time in seconds, after which a
                TLS-level message will be sent to test the
                aliveness of the TLS server if no data has been
                received from the TLS server.";
           }
           leaf max-attempts {
             type uint8;
             default "3";
             description
               "Sets the maximum number of sequential keepalive
                messages that can fail to obtain a response from
                the TLS server before assuming the TLS server is
                no longer alive.";
           }
         }
       }
     } // grouping tls-client-grouping

   }
   <CODE ENDS>

4.  The "ietf-tls-server" Module

   This section defines a YANG 1.1 module called "ietf-tls-server".  A
   high-level overview of the module is provided in Section 4.1.
   Examples illustrating the module's use are provided in Section 4.2
   ("Example Usage").  The YANG module itself is defined in Section 4.3.

4.1.  Data Model Overview

   This section provides an overview of the "ietf-tls-server" module in
   terms of its features and groupings.

4.1.1.  Features

   The following diagram lists all the "feature" statements defined in
   the "ietf-tls-server" module:

   Features:
     +-- tls-server-keepalives
     +-- server-ident-x509-cert
     +-- server-ident-raw-public-key
     +-- server-ident-psk
     +-- client-auth-supported
     +-- client-auth-x509-cert
     +-- client-auth-raw-public-key
     +-- client-auth-psk

   The diagram above uses syntax that is similar to but not defined in
   [RFC8340].

   Please refer to the YANG module for a description of each feature.

4.1.2.  Groupings

   The "ietf-tls-server" module defines the following "grouping"
   statement:

   *  tls-server-grouping

   This grouping is presented in the following subsection.

4.1.2.1.  The "tls-server-grouping" Grouping

   The following tree diagram [RFC8340] illustrates the "tls-server-
   grouping" grouping:

   =============== NOTE: '\' line wrapping per RFC 8792 ================

     grouping tls-server-grouping:
       +-- server-identity
       |  +-- (auth-type)
       |     +--:(certificate) {server-ident-x509-cert}?
       |     |  +-- certificate
       |     |     +---u ks:inline-or-keystore-end-entity-cert-with-key\
   -grouping
       |     +--:(raw-private-key) {server-ident-raw-public-key}?
       |     |  +-- raw-private-key
       |     |     +---u ks:inline-or-keystore-asymmetric-key-grouping
       |     +--:(tls12-psk) {server-ident-tls12-psk}?
       |     |  +-- tls12-psk
       |     |     +---u ks:inline-or-keystore-symmetric-key-grouping
       |     |     +-- id-hint?
       |     |             string
       |     +--:(tls13-epsk) {server-ident-tls13-epsk}?
       |        +-- tls13-epsk
       |           +---u ks:inline-or-keystore-symmetric-key-grouping
       |           +-- external-identity
       |           |       string
       |           +-- hash?
       |           |       tlscmn:epsk-supported-hash
       |           +-- context?
       |           |       string
       |           +-- target-protocol?
       |           |       uint16
       |           +-- target-kdf?
       |                   uint16
       +-- client-authentication! {client-auth-supported}?
       |  +-- ca-certs! {client-auth-x509-cert}?
       |  |  +---u ts:inline-or-truststore-certs-grouping
       |  +-- ee-certs! {client-auth-x509-cert}?
       |  |  +---u ts:inline-or-truststore-certs-grouping
       |  +-- raw-public-keys! {client-auth-raw-public-key}?
       |  |  +---u ts:inline-or-truststore-public-keys-grouping
       |  +-- tls12-psks?        empty {client-auth-tls12-psk}?
       |  +-- tls13-epsks?       empty {client-auth-tls13-epsk}?
       +-- hello-params {tlscmn:hello-params}?
       |  +---u tlscmn:hello-params-grouping
       +-- keepalives {tls-server-keepalives}?
          +-- peer-allowed-to-send?   empty
          +-- test-peer-aliveness!
             +-- max-wait?       uint16
             +-- max-attempts?   uint8

   Comments:

   *  The "server-identity" node configures identity credentials, each
      of which is enabled by a "feature".

   *  The "client-authentication" node, which is optionally configured
      (as client authentication MAY occur at a higher protocol layer),
      configures trust anchors for authenticating the TLS client, with
      each option enabled by a "feature" statement.

   *  The "hello-params" node, which must be enabled by a feature,
      configures parameters for the TLS sessions established by this
      configuration.

   *  The "keepalives" node, which must be enabled by a feature,
      configures a flag enabling the TLS client to test the aliveness of
      the TLS server as well as a "presence" container to test the
      aliveness of the TLS client.  The aliveness-tests occur at the TLS
      protocol layer.

   *  For the referenced grouping statement(s):

      -  The "inline-or-keystore-end-entity-cert-with-key-grouping"
         grouping is discussed in Section 2.1.3.6 of [RFC9642].
      -  The "inline-or-keystore-asymmetric-key-grouping" grouping is
         discussed in Section 2.1.3.4 of [RFC9642].
      -  The "inline-or-keystore-symmetric-key-grouping" grouping is
         discussed in Section 2.1.3.3 of [RFC9642].
      -  The "inline-or-truststore-public-keys-grouping" grouping is
         discussed in Section 2.1.3.4 of [RFC9641].
      -  The "inline-or-truststore-certs-grouping" grouping is discussed
         in Section 2.1.3.3 of [RFC9641].
      -  The "hello-params-grouping" grouping is discussed in
         Section 2.1.3.1 in this document.

4.1.3.  Protocol-Accessible Nodes

   The "ietf-tls-server" module defines only "grouping" statements that
   are used by other modules to instantiate protocol-accessible nodes.
   Thus, this module does not itself define any protocol-accessible
   nodes when implemented.

4.2.  Example Usage

   This section presents two examples showing the "tls-server-grouping"
   grouping populated with some data.  These examples are effectively
   the same except the first configures the server identity using a
   local key while the second uses a key configured in a keystore.  Both
   examples are consistent with the examples presented in Section 2.2.1
   of [RFC9641] and Section 2.2.1 of [RFC9642].

   The following configuration example uses inline-definitions for the
   server identity and client authentication:

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <!-- The outermost element below doesn't exist in the data model. -->
   <!--  It simulates if the "grouping" were a "container" instead.  -->

   <tls-server
     xmlns="urn:ietf:params:xml:ns:yang:ietf-tls-server"
     xmlns:ct="urn:ietf:params:xml:ns:yang:ietf-crypto-types">

       <!-- how this server will authenticate itself to the client -->
       <server-identity>
           <certificate>
             <inline-definition>
                 <private-key-format>ct:rsa-private-key-format</private\
   -key-format>
                 <cleartext-private-key>BASE64VALUE=</cleartext-private\
   -key>
                 <cert-data>BASE64VALUE=</cert-data>
               </inline-definition>
           </certificate>
       </server-identity>

       <!-- which certificates will this server trust -->
       <client-authentication>
           <ca-certs>
               <inline-definition>
                   <certificate>
                       <name>Identity Cert Issuer #1</name>
                       <cert-data>BASE64VALUE=</cert-data>
                   </certificate>
                   <certificate>
                       <name>Identity Cert Issuer #2</name>
                       <cert-data>BASE64VALUE=</cert-data>
                   </certificate>
               </inline-definition>
           </ca-certs>
           <ee-certs>
               <inline-definition>
                   <certificate>
                       <name>Application #1</name>
                       <cert-data>BASE64VALUE=</cert-data>
                   </certificate>
                   <certificate>
                       <name>Application #2</name>
                       <cert-data>BASE64VALUE=</cert-data>
                   </certificate>
               </inline-definition>
           </ee-certs>
           <raw-public-keys>
               <inline-definition>
                   <public-key>
                       <name>User A</name>
                       <public-key-format>ct:subject-public-key-info-fo\
   rmat</public-key-format>
                       <public-key>BASE64VALUE=</public-key>
                   </public-key>
                   <public-key>
                       <name>User B</name>
                       <public-key-format>ct:subject-public-key-info-fo\
   rmat</public-key-format>
                       <public-key>BASE64VALUE=</public-key>
                   </public-key>
               </inline-definition>
           </raw-public-keys>
           <tls12-psks/>
           <tls13-epsks/>
       </client-authentication>

       <keepalives>
           <peer-allowed-to-send/>
       </keepalives>

   </tls-server>

   The following configuration example uses central-keystore-references
   for the server identity and central-truststore-references for client
   authentication from the keystore:

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <!-- The outermost element below doesn't exist in the data model. -->
   <!--  It simulates if the "grouping" were a "container" instead.  -->

   <tls-server xmlns="urn:ietf:params:xml:ns:yang:ietf-tls-server">

       <!-- how this server will authenticate itself to the client -->
       <server-identity>
           <certificate>
               <central-keystore-reference>
                   <asymmetric-key>rsa-asymmetric-key</asymmetric-key>
                   <certificate>ex-rsa-cert</certificate>
               </central-keystore-reference>
           </certificate>
       </server-identity>

       <!-- which certificates will this server trust -->
       <client-authentication>
           <ca-certs>
               <central-truststore-reference>trusted-client-ca-certs</c\
   entral-truststore-reference>
           </ca-certs>
           <ee-certs>
               <central-truststore-reference>trusted-client-ee-certs</c\
   entral-truststore-reference>
           </ee-certs>
           <raw-public-keys>
               <central-truststore-reference>Raw Public Keys for TLS Cl\
   ients</central-truststore-reference>
           </raw-public-keys>
           <tls12-psks/>
           <tls13-epsks/>
       </client-authentication>

       <keepalives>
           <peer-allowed-to-send/>
       </keepalives>

   </tls-server>

4.3.  YANG Module

   This YANG module has normative references to [RFC4279], [RFC5280],
   [RFC6520], [RFC7250], [RFC9640], [RFC9641], and [RFC9642] and
   informative references to [RFC5056], [RFC5246], [RFC8446], [RFC9258],
   and [RFC9257].

   <CODE BEGINS> file "ietf-tls-server@2024-10-10.yang"
   module ietf-tls-server {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-tls-server";
     prefix tlss;

     import ietf-netconf-acm {
       prefix nacm;
       reference
         "RFC 8341: Network Configuration Access Control Model";
     }
     import ietf-crypto-types {
       prefix ct;
       reference
         "RFC 9640: YANG Data Types and Groupings for Cryptography";
     }
     import ietf-truststore {
       prefix ts;
       reference
         "RFC 9641: A YANG Data Model for a Truststore";
     }
     import ietf-keystore {
       prefix ks;
       reference
         "RFC 9642: A YANG Data Model for a Keystore";
     }
     import ietf-tls-common {
       prefix tlscmn;
       reference
         "RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
     }

     organization
       "IETF NETCONF (Network Configuration) Working Group";
     contact
       "WG List:  NETCONF WG list <mailto:netconf@ietf.org>
        WG Web:   https://datatracker.ietf.org/wg/netconf
        Author:   Kent Watsen <mailto:kent+ietf@watsen.net>
        Author:   Jeff Hartley <mailto:intensifysecurity@gmail.com>";
     description
       "This module defines reusable groupings for TLS servers that
        can be used as a basis for specific TLS server instances.

        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 9645
        (https://www.rfc-editor.org/info/rfc9645); see the RFC
        itself for full legal notices.";

     revision 2024-10-10 {
       description
         "Initial version.";
       reference
         "RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
     }

     // Features

     feature tls-server-keepalives {
       description
         "Per-socket TLS keepalive parameters are configurable for
          TLS servers on the server implementing this feature.";
     }

     feature server-ident-x509-cert {
       description
         "Indicates that the server supports identifying itself
          using X.509 certificates.";
       reference
         "RFC 5280:
            Internet X.509 Public Key Infrastructure Certificate
            and Certificate Revocation List (CRL) Profile";
     }

     feature server-ident-raw-public-key {
       description
         "Indicates that the server supports identifying itself
          using raw public keys.";
       reference
         "RFC 7250:
            Using Raw Public Keys in Transport Layer Security (TLS)
            and Datagram Transport Layer Security (DTLS)";
     }

     feature server-ident-tls12-psk {
       if-feature "tlscmn:tls12";
       description
         "Indicates that the server supports identifying itself
          using TLS 1.2 PSKs (pre-shared or pairwise symmetric keys).";
       reference
         "RFC 4279:
            Pre-Shared Key Ciphersuites for Transport Layer Security
            (TLS)";
     }

     feature server-ident-tls13-epsk {
       if-feature "tlscmn:tls13";
       description
         "Indicates that the server supports identifying itself
          using TLS 1.3 External PSKs (pre-shared keys).";
       reference
         "RFC 8446:
            The Transport Layer Security (TLS) Protocol Version 1.3";
     }

     feature client-auth-supported {
       description
         "Indicates that the configuration for how to authenticate
          clients can be configured herein.  TLS-level client
          authentication may not be needed when client authentication
          is expected to occur only at another protocol layer.";
     }

     feature client-auth-x509-cert {
       description
         "Indicates that the server supports authenticating clients
          using X.509 certificates.";
       reference
         "RFC 5280:
            Internet X.509 Public Key Infrastructure Certificate
            and Certificate Revocation List (CRL) Profile";
     }

     feature client-auth-raw-public-key {
       description
         "Indicates that the server supports authenticating clients
          using raw public keys.";
       reference
         "RFC 7250:
            Using Raw Public Keys in Transport Layer Security (TLS)
            and Datagram Transport Layer Security (DTLS)";
     }

     feature client-auth-tls12-psk {
       description
         "Indicates that the server supports authenticating clients
          using PSKs (pre-shared or pairwise symmetric keys).";
       reference
         "RFC 4279:
            Pre-Shared Key Ciphersuites for Transport Layer Security
            (TLS)";
     }

     feature client-auth-tls13-epsk {
       description
         "Indicates that the server supports authenticating clients
          using TLS 1.3 External PSKs (pre-shared keys).";
       reference
         "RFC 8446:
            The Transport Layer Security (TLS) Protocol Version 1.3";
     }

     // Groupings

     grouping tls-server-grouping {
       description
         "A reusable grouping for configuring a TLS server without
          any consideration for how underlying TCP sessions are
          established.

          Note that this grouping uses fairly typical descendant
          node names such that a stack of 'uses' statements will
          have name conflicts.  It is intended that the consuming
          data model will resolve the issue (e.g., by wrapping
          the 'uses' statement in a container called
          'tls-server-parameters').  This model purposely does
          not do this itself so as to provide maximum flexibility
          to consuming models.";
       container server-identity {
         nacm:default-deny-write;
         description
           "A locally defined or referenced End-Entity (EE) certificate,
            including any configured intermediate certificates, that
            the TLS server will present when establishing a TLS
            connection in its Certificate message, as defined in
            Section 7.4.2 of RFC 5246 and Section 4.4.2 of RFC 8446.";
         reference
           "RFC 5246: The Transport Layer Security (TLS) Protocol
                      Version 1.2
            RFC 8446: The Transport Layer Security (TLS) Protocol
                      Version 1.3
            RFC 9642: A YANG Data Model for a Keystore";
         choice auth-type {
           mandatory true;
           description
             "A choice amongst authentication types, of which one must
              be enabled (via its associated 'feature') and selected.";
           case certificate {
             if-feature "server-ident-x509-cert";
             container certificate {
               description
                 "Specifies the server identity using a certificate.";
               uses "ks:inline-or-keystore-end-entity-cert-with-key-"
                  + "grouping" {
                 refine "inline-or-keystore/inline/inline-definition" {
                   must 'not(public-key-format) or derived-from-or-self'
                      + '(public-key-format,'
                      + ' "ct:subject-public-'
                      + 'key-info-format")';
                 }
                 refine "inline-or-keystore/central-keystore/"
                      + "central-keystore-reference/asymmetric-key" {
                   must 'not(deref(.)/../ks:public-key-format) or '
                      + 'derived-from-or-self(deref(.)/../ks:public-key'
                      + '-format, "ct:subject-public-key-info-format")';
                 }
               }
             }
           }
           case raw-private-key {
             if-feature "server-ident-raw-public-key";
             container raw-private-key {
               description
                 "Specifies the server identity using a raw
                  private key.";
               uses ks:inline-or-keystore-asymmetric-key-grouping {
                 refine "inline-or-keystore/inline/inline-definition" {
                   must 'not(public-key-format) or derived-from-or-self'
                      + '(public-key-format,'
                      + ' "ct:subject-public-'
                      + 'key-info-format")';
                 }
                 refine "inline-or-keystore/central-keystore/"
                      + "central-keystore-reference" {
                   must 'not(deref(.)/../ks:public-key-format) or '
                      + 'derived-from-or-self(deref(.)/../ks:public-key'
                      + '-format, "ct:subject-public-key-info-format")';
                 }
               }
             }
           }
           case tls12-psk {
             if-feature "server-ident-tls12-psk";
             container tls12-psk {
               description
                 "Specifies the server identity using a PSK (pre-shared
                  or pairwise symmetric key).";
               uses ks:inline-or-keystore-symmetric-key-grouping;
               leaf id-hint {
                 type string;
                 description
                   "The key 'psk_identity_hint' value used in the TLS
                    'ServerKeyExchange' message.";
                 reference
                   "RFC 4279: Pre-Shared Key Ciphersuites for
                              Transport Layer Security (TLS)";
               }
             }
           }
           case tls13-epsk {
             if-feature "server-ident-tls13-epsk";
             container tls13-epsk {
               description
                 "An External Pre-Shared Key (EPSK) is established
                  or provisioned out of band, i.e., not from a TLS
                  connection.  An EPSK is a tuple of (Base Key,
                  External Identity, Hash).  EPSKs MUST NOT be
                  imported for (D)TLS 1.2 or prior versions.
                  When PSKs are provisioned out of band, the PSK
                  identity and the KDF hash algorithm to be used
                  with the PSK MUST also be provisioned.

                  The structure of this container is designed to
                  satisfy the requirements in Section 4.2.11 of
                  RFC 8446, the recommendations from Section 6 of
                  RFC 9257, and the EPSK input fields detailed in
                  Section 5.1 of RFC 9258.  The base-key is based
                  upon 'ks:inline-or-keystore-symmetric-key-grouping'
                  in order to provide users with flexible and
                  secure storage options.";
               reference
                 "RFC 8446: The Transport Layer Security (TLS)
                            Protocol Version 1.3
                  RFC 9257: Guidance for External Pre-Shared Key
                            (PSK) Usage in TLS
                  RFC 9258: Importing External Pre-Shared Keys
                            (PSKs) for TLS 1.3";
               uses ks:inline-or-keystore-symmetric-key-grouping;
               leaf external-identity {
                 type string;
                 mandatory true;
                 description
                   "As per Section 4.2.11 of RFC 8446 and Section 4.1
                    of RFC 9257, a sequence of bytes used to identify
                    an EPSK.  A label for a pre-shared key established
                    externally.";
                 reference
                   "RFC 8446: The Transport Layer Security (TLS)
                              Protocol Version 1.3
                    RFC 9257: Guidance for External Pre-Shared Key
                              (PSK) Usage in TLS";
               }
               leaf hash {
                 type tlscmn:epsk-supported-hash;
                 default "sha-256";
                 description
                   "As per Section 4.2.11 of RFC 8446, for EPSKs,
                    the hash algorithm MUST be set when the PSK is
                    established; otherwise, default to SHA-256 if
                    no such algorithm is defined.  The server MUST
                    ensure that it selects a compatible PSK (if any)
                    and cipher suite.  Each PSK MUST only be used
                    with a single hash function.";
                 reference
                   "RFC 8446: The Transport Layer Security (TLS)
                              Protocol Version 1.3";
               }
               leaf context {
                 type string;
                 description
                   "As per Section 5.1 of RFC 9258, context MUST
                    include the context used to determine the EPSK,
                    if any exists.  For example, context may include
                    information about peer roles or identities
                    to mitigate Selfie-style reflection attacks.
                    Since the EPSK is a key derived from an external
                    protocol or sequence of protocols, context MUST
                    include a channel binding for the deriving
                    protocols (see RFC 5056).  The details of this
                    binding are protocol specific and out of scope
                    for this document.";
                 reference
                   "RFC 9258: Importing External Pre-Shared Keys
                              (PSKs) for TLS 1.3";
               }
               leaf target-protocol {
                 type uint16;
                 description
                   "As per Section 3.1 of RFC 9258, the protocol
                    for which a PSK is imported for use.";
                 reference
                   "RFC 9258: Importing External Pre-Shared Keys
                              (PSKs) for TLS 1.3";
               }
               leaf target-kdf {
                 type uint16;
                 description
                   "As per Section 3 of RFC 9258, the KDF for
                    which a PSK is imported for use.";
                 reference
                   "RFC 9258: Importing External Pre-Shared Keys
                              (PSKs) for TLS 1.3";
               }
             }
           }
         }
       } // container server-identity
       container client-authentication {
         if-feature "client-auth-supported";
         nacm:default-deny-write;
         must "ca-certs or ee-certs or raw-public-keys or tls12-psks
                       or tls13-epsks";
         presence "Indicates that client authentication is supported
                   (i.e., that the server will request clients send
                   certificates).  If not configured, the TLS server
                   SHOULD NOT request that TLS clients provide
                   authentication credentials.";
         description
           "Specifies how the TLS server can authenticate TLS clients.
            Any combination of credentials is additive and unordered.

            Note that no configuration is required for authentication
            based on PSK (pre-shared or pairwise symmetric key) as the
            the key is necessarily the same as configured in the
            '../server-identity' node.";
         container ca-certs {
           if-feature "client-auth-x509-cert";
           presence "Indicates that Certification Authority (CA)
                     certificates have been configured.  This
                     statement is present so the mandatory
                     descendant nodes do not imply that this node
                     must be configured.";
           description
             "A set of CA certificates used by the TLS server to
              authenticate TLS client certificates.  A client
              certificate is authenticated if it has a valid chain
              of trust to a configured CA certificate.";
           reference
             "RFC 9641: A YANG Data Model for a Truststore";
           uses ts:inline-or-truststore-certs-grouping;
         }
         container ee-certs {
           if-feature "client-auth-x509-cert";
           presence "Indicates that EE certificates have been
                     configured.  This statement is present so the
                     mandatory descendant nodes do not imply that
                     this node must be configured.";
           description
             "A set of client certificates (i.e., EE certificates)
              used by the TLS server to authenticate
              certificates presented by TLS clients.  A client
              certificate is authenticated if it is an exact
              match to a configured client certificate.";
           reference
             "RFC 9641: A YANG Data Model for a Truststore";
           uses ts:inline-or-truststore-certs-grouping;
         }
         container raw-public-keys {
           if-feature "client-auth-raw-public-key";
           presence "Indicates that raw public keys have been
                     configured.  This statement is present so
                     the mandatory descendant nodes do not imply
                     that this node must be configured.";
           description
             "A set of raw public keys used by the TLS server to
              authenticate raw public keys presented by the TLS
              client.  A raw public key is authenticated if it
              is an exact match to a configured raw public key.";
           reference
             "RFC 9641: A YANG Data Model for a Truststore";
           uses ts:inline-or-truststore-public-keys-grouping {
             refine "inline-or-truststore/inline/inline-definition/"
                  + "public-key" {
               must 'derived-from-or-self(public-key-format,'
                  + ' "ct:subject-public-key-info-format")';
             }
             refine "inline-or-truststore/central-truststore/"
                  + "central-truststore-reference" {
               must 'not(deref(.)/../ts:public-key/ts:public-key-'
                  + 'format[not(derived-from-or-self(., "ct:subject-'
                  + 'public-key-info-format"))])';
             }
           }
         }
         leaf tls12-psks {
           if-feature "client-auth-tls12-psk";
           type empty;
           description
             "Indicates that the TLS server can authenticate TLS clients
              using configured PSKs (pre-shared or pairwise symmetric
              keys).

              No configuration is required since the PSK value is the
              same as PSK value configured in the 'server-identity'
              node.";
         }
         leaf tls13-epsks {
           if-feature "client-auth-tls13-epsk";
           type empty;
           description
             "Indicates that the TLS 1.3 server can authenticate TLS
              clients using configured External PSKs (pre-shared keys).

              No configuration is required since the PSK value is the
              same as PSK value configured in the 'server-identity'
              node.";
         }
       } // container client-authentication
       container hello-params {
         nacm:default-deny-write;
         if-feature "tlscmn:hello-params";
         uses tlscmn:hello-params-grouping;
         description
           "Configurable parameters for the TLS hello message.";
       } // container hello-params
       container keepalives {
         nacm:default-deny-write;
         if-feature "tls-server-keepalives";
         description
           "Configures the keepalive policy for the TLS server.";
         leaf peer-allowed-to-send {
           type empty;
           description
             "Indicates that the remote TLS client is allowed to send
              HeartbeatRequest messages, as defined by RFC 6520,
              to this TLS server.";
           reference
             "RFC 6520: Transport Layer Security (TLS) and Datagram
              Transport Layer Security (DTLS) Heartbeat Extension";
         }
         container test-peer-aliveness {
           presence "Indicates that the TLS server proactively tests the
                     aliveness of the remote TLS client.";
           description
             "Configures the keepalive policy to proactively test
              the aliveness of the TLS client.  An unresponsive
              TLS client is dropped after approximately max-wait
              * max-attempts seconds.";
           leaf max-wait {
             type uint16 {
               range "1..max";
             }
             units "seconds";
             default "30";
             description
               "Sets the amount of time in seconds, after which a
                TLS-level message will be sent to test the
                aliveness of the TLS client if no data has been
                received from the TLS client.";
           }
           leaf max-attempts {
             type uint8;
             default "3";
             description
               "Sets the maximum number of sequential keepalive
                messages that can fail to obtain a response from
                the TLS client before assuming the TLS client is
                no longer alive.";
           }
         }
       } // container keepalives
     } // grouping tls-server-grouping

   }
   <CODE ENDS>

5.  Security Considerations

   The three IETF YANG modules in this document define groupings and
   will not be deployed as standalone modules.  Their security
   implications may be context dependent based on their use in other
   modules.  The designers of modules that import these grouping must
   conduct their own analysis of the security considerations.

5.1.  Considerations for the "iana-tls-cipher-suite-algs" YANG Module

   This section is modeled after the template defined in Section 3.7.1
   of [RFC8407].

   The "iana-tls-cipher-suite-algs" YANG module defines a data model
   that is designed to be accessed via YANG-based management protocols,
   such as NETCONF [RFC6241] and RESTCONF [RFC8040].  These protocols
   have mandatory-to-implement secure transport layers (e.g., Secure
   Shell (SSH) [RFC4252], TLS [RFC8446], and QUIC [RFC9000]) and
   mandatory-to-implement mutual authentication.

   The Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular users to a
   preconfigured subset of all available protocol operations and
   content.

   This YANG module defines YANG enumerations, for a public IANA-
   maintained registry.

   YANG enumerations are not security-sensitive, as they are statically
   defined in the publicly accessible YANG module.  IANA MAY deprecate
   and/or obsolete enumerations over time as needed to address security
   issues found in the algorithms.

   This module does not define any writable nodes, RPCs, actions, or
   notifications, and thus the security considerations for such are not
   provided here.

5.2.  Considerations for the "ietf-tls-common" YANG Module

   This section is modeled after the template defined in Section 3.7.1
   of [RFC8407].

   The "ietf-tls-common" YANG module defines a data model that is
   designed to be accessed via YANG-based management protocols, such as
   NETCONF [RFC6241] and RESTCONF [RFC8040].  These protocols have
   mandatory-to-implement secure transport layers (e.g., Secure Shell
   (SSH) [RFC4252], TLS [RFC8446], and QUIC [RFC9000]) and mandatory-to-
   implement mutual authentication.

   The Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular users to a
   preconfigured subset of all available protocol operations and
   content.

   Please be aware that this YANG module uses groupings from other YANG
   modules that define nodes that may be considered sensitive or
   vulnerable in network environments.  Please review the Security
   Considerations for dependent YANG modules for information as to which
   nodes may be considered sensitive or vulnerable in network
   environments.

   None of the readable data nodes defined in this YANG module are
   considered sensitive or vulnerable in network environments.  The NACM
   "default-deny-all" extension has not been set for any data nodes
   defined in this module.

   None of the writable data nodes defined in this YANG module are
   considered sensitive or vulnerable in network environments.  The NACM
   "default-deny-write" extension has not been set for any data nodes
   defined in this module.

   This module defines the "generate-asymmetric-key-pair" RPC that may,
   if the "ct:cleartext-private-keys" feature is enabled and the client
   requests it, return the private clear in cleartext form.  It is NOT
   RECOMMENDED for private keys to pass the server's security perimeter.

   This module does not define any actions or notifications, and thus
   the security considerations for such are not provided here.

5.3.  Considerations for the "ietf-tls-client" YANG Module

   This section is modeled after the template defined in Section 3.7.1
   of [RFC8407].

   The "ietf-tls-client" YANG module defines a data model that is
   designed to be accessed via YANG-based management protocols, such as
   NETCONF [RFC6241] and RESTCONF [RFC8040].  These protocols have
   mandatory-to-implement secure transport layers (e.g., Secure Shell
   (SSH) [RFC4252], TLS [RFC8446], and QUIC [RFC9000]) and mandatory-to-
   implement mutual authentication.

   The Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular users to a
   preconfigured subset of all available protocol operations and
   content.

   Please be aware that this YANG module uses groupings from other YANG
   modules that define nodes that may be considered sensitive or
   vulnerable in network environments.  Please review the Security
   Considerations for dependent YANG modules for information as to which
   nodes may be considered sensitive or vulnerable in network
   environments.

   None of the readable data nodes defined in this YANG module are
   considered sensitive or vulnerable in network environments.  The NACM
   "default-deny-all" extension has not been set for any data nodes
   defined in this module.

   All the writable data nodes defined by this module may be considered
   sensitive or vulnerable in some network environments.  For instance,
   any modification to a key or reference to a key may dramatically
   alter the implemented security policy.  For this reason, the NACM
   extension "default-deny-write" has been set for all data nodes
   defined in this module.

   This module does not define any RPCs, actions, or notifications, and
   thus the security considerations for such are not provided here.

5.4.  Considerations for the "ietf-tls-server" YANG Module

   This section is modeled after the template defined in Section 3.7.1
   of [RFC8407].

   The "ietf-tls-server" YANG module defines a data model that is
   designed to be accessed via YANG-based management protocols, such as
   NETCONF [RFC6241] and RESTCONF [RFC8040].  These protocols have
   mandatory-to-implement secure transport layers (e.g., Secure Shell
   (SSH) [RFC4252], TLS [RFC8446], and QUIC [RFC9000]) and mandatory-to-
   implement mutual authentication.

   The Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular users to a
   preconfigured subset of all available protocol operations and
   content.

   Please be aware that this YANG module uses groupings from other YANG
   modules that define nodes that may be considered sensitive or
   vulnerable in network environments.  Please review the Security
   Considerations for dependent YANG modules for information as to which
   nodes may be considered sensitive or vulnerable in network
   environments.

   None of the readable data nodes defined in this YANG module are
   considered sensitive or vulnerable in network environments.  The NACM
   "default-deny-all" extension has not been set for any data nodes
   defined in this module.

   Please be aware that this module uses the "key" and "private-key"
   nodes from the "ietf-crypto-types" module [RFC9640], where said nodes
   have the NACM extension "default-deny-all" set, thus preventing
   unrestricted read access to the cleartext key values.

   All the writable data nodes defined by this module may be considered
   sensitive or vulnerable in some network environments.  For instance,
   any modification to a key or reference to a key may dramatically
   alter the implemented security policy.  For this reason, the NACM
   extension "default-deny-write" has been set for all data nodes
   defined in this module.

   This module does not define any RPCs, actions, or notifications, and
   thus the security considerations for such are not provided here.

6.  IANA Considerations

6.1.  The IETF XML Registry

   IANA has registered the following four URIs in the "ns" registry of
   the "IETF XML Registry" [RFC3688].

   URI:  urn:ietf:params:xml:ns:yang:iana-tls-cipher-suite-algs
   Registrant Contact:  The IESG
   XML:  N/A; the requested URI is an XML namespace.

   URI:  urn:ietf:params:xml:ns:yang:ietf-tls-common
   Registrant Contact:  The IESG
   XML:  N/A; the requested URI is an XML namespace.

   URI:  urn:ietf:params:xml:ns:yang:ietf-tls-client
   Registrant Contact:  The IESG
   XML:  N/A; the requested URI is an XML namespace.

   URI:  urn:ietf:params:xml:ns:yang:ietf-tls-server
   Registrant Contact:  The IESG
   XML:  N/A; the requested URI is an XML namespace.

6.2.  The YANG Module Names Registry

   IANA has registered the following four YANG modules in the "YANG
   Module Names" registry [RFC6020].

   name:  iana-tls-cipher-suite-algs
   Maintained by IANA:  Y
   namespace:  urn:ietf:params:xml:ns:yang:iana-tls-cipher-suite-algs
   prefix:  tlscsa
   reference:  RFC 9645

   name:  ietf-tls-common
   Maintained by IANA:  N
   namespace:  urn:ietf:params:xml:ns:yang:ietf-tls-common
   prefix:  tlscmn
   reference:  RFC 9645

   name:  ietf-tls-client
   Maintained by IANA:  N
   namespace:  urn:ietf:params:xml:ns:yang:ietf-tls-client
   prefix:  tlsc
   reference:  RFC 9645

   name:  ietf-tls-server
   Maintained by IANA:  N
   namespace:  urn:ietf:params:xml:ns:yang:ietf-tls-server
   prefix:  tlss
   reference:  RFC 9645

6.3.  Considerations for the "iana-tls-cipher-suite-algs" YANG Module

   This section follows the template defined in Section 4.30.3.1 of
   [RFC8407BIS].

   IANA used the script in Appendix A to generate the IANA-maintained
   "iana-tls-cipher-suite-algs" YANG module.  The YANG module is
   available from the "YANG Parameters" registry [IANA-YANG-PARAMETERS].

   IANA has added the following note to the registry:

   |  New values must not be directly added to the "iana-tls-cipher-
   |  suite-algs" YANG module.  They must instead be added to the "TLS
   |  Cipher Suites" registry in the "Transport Layer Security (TLS)
   |  Parameters" registry group [IANA-CIPHER-ALGS].

   When a value is added to the "TLS Cipher Suites" registry, a new
   "enum" statement must be added to the "iana-tls-cipher-suite-algs"
   YANG module.  The "enum" statement, and substatements thereof, should
   be defined as follows:

   enum
      Replicates a name from the registry.

   value
      Contains the decimal value of the IANA-assigned value.

   status
      Include only if a registration has been deprecated or obsoleted.
      An IANA "Recommended" value "N" maps to YANG status "deprecated".
      Since the registry is unable to express a logical "MUST NOT"
      recommendation, there is no mapping to YANG status "obsolete",
      which is unfortunate given the moving of single-DES and
      International Data Encryption Algorithm (IDEA) TLS cipher suites
      to Historic [RFC8996].

   description
      Contains "Enumeration for the 'TLS_FOO' algorithm", where
      "TLS_FOO" is a placeholder for the algorithm's name (e.g.,
      "TLS_PSK_WITH_AES_256_CBC_SHA").

   reference
      Replicates the reference(s) from the registry with the title of
      the document(s) added.

   Unassigned or reserved values are not present in the module.

   When the "iana-tls-cipher-suite-algs" YANG module is updated, a new
   "revision" statement with a unique revision date must be added in
   front of the existing revision statements.  The "revision" must have
   a "description" statement explaining why the the update occurred and
   must have a "reference" substatement that points to the document
   defining the registry update that resulted in this change.  For
   instance:

   revision 2024-10-10 {
       description
           "This update reflects the update made to the underlying
            'Foo Bar' registry per RFC XXXX.";
       reference
           "RFC XXXX: Extend the Foo Bar Registry
                      to Support Something Important";
   }

   IANA has added the following note to the "TLS Cipher Suites" registry
   under the "Transport Layer Security (TLS) Parameters" registry group
   [IANA-CIPHER-ALGS].

   |  When this registry is modified, the YANG module "iana-tls-cipher-
   |  suite-algs" [IANA-YANG-PARAMETERS] must be updated as defined in
   |  RFC 9645.

7.  References

7.1.  Normative References

   [FIPS180-4]
              National Institute of Standards and Technology (NIST),
              "Secure Hash Standard (SHS)", FIPS PUB 180-4,
              DOI 10.6028/NIST.FIPS.180-4, August 2015,
              <https://nvlpubs.nist.gov/nistpubs/FIPS/
              NIST.FIPS.180-4.pdf>.

   [FIPS186-5]
              National Institute of Standards and Technology (NIST),
              "Digital Signature Standard (DSS)", FIPS 186-5,
              DOI 10.6028/NIST.FIPS.186-5, February 2023,
              <https://nvlpubs.nist.gov/nistpubs/FIPS/
              NIST.FIPS.186-5.pdf>.

   [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>.

   [RFC4252]  Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
              January 2006, <https://www.rfc-editor.org/info/rfc4252>.

   [RFC4279]  Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
              Ciphersuites for Transport Layer Security (TLS)",
              RFC 4279, DOI 10.17487/RFC4279, December 2005,
              <https://www.rfc-editor.org/info/rfc4279>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/info/rfc5280>.

   [RFC5288]  Salowey, J., Choudhury, A., and D. McGrew, "AES Galois
              Counter Mode (GCM) Cipher Suites for TLS", RFC 5288,
              DOI 10.17487/RFC5288, August 2008,
              <https://www.rfc-editor.org/info/rfc5288>.

   [RFC5289]  Rescorla, E., "TLS Elliptic Curve Cipher Suites with SHA-
              256/384 and AES Galois Counter Mode (GCM)", RFC 5289,
              DOI 10.17487/RFC5289, August 2008,
              <https://www.rfc-editor.org/info/rfc5289>.

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

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

   [RFC6520]  Seggelmann, R., Tuexen, M., and M. Williams, "Transport
              Layer Security (TLS) and Datagram Transport Layer Security
              (DTLS) Heartbeat Extension", RFC 6520,
              DOI 10.17487/RFC6520, February 2012,
              <https://www.rfc-editor.org/info/rfc6520>.

   [RFC7250]  Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
              Weiler, S., and T. Kivinen, "Using Raw Public Keys in
              Transport Layer Security (TLS) and Datagram Transport
              Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
              June 2014, <https://www.rfc-editor.org/info/rfc7250>.

   [RFC7589]  Badra, M., Luchuk, A., and J. Schoenwaelder, "Using the
              NETCONF Protocol over Transport Layer Security (TLS) with
              Mutual X.509 Authentication", RFC 7589,
              DOI 10.17487/RFC7589, June 2015,
              <https://www.rfc-editor.org/info/rfc7589>.

   [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>.

   [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>.

   [RFC8422]  Nir, Y., Josefsson, S., and M. Pegourie-Gonnard, "Elliptic
              Curve Cryptography (ECC) Cipher Suites for Transport Layer
              Security (TLS) Versions 1.2 and Earlier", RFC 8422,
              DOI 10.17487/RFC8422, August 2018,
              <https://www.rfc-editor.org/info/rfc8422>.

   [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>.

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/info/rfc9000>.

   [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>.

   [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>.

7.2.  Informative References

   [HTTP-CLIENT-SERVER]
              Watsen, K., "YANG Groupings for HTTP Clients and HTTP
              Servers", Work in Progress, Internet-Draft, draft-ietf-
              netconf-http-client-server-23, 15 August 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
              http-client-server-23>.

   [IANA-CIPHER-ALGS]
              IANA, "TLS Cipher Suites",
              <https://www.iana.org/assignments/tls-parameters/>.

   [IANA-YANG-PARAMETERS]
              IANA, "YANG Parameters",
              <https://www.iana.org/assignments/yang-parameters>.

   [NETCONF-CLIENT-SERVER]
              Watsen, K., "NETCONF Client and Server Models", Work in
              Progress, Internet-Draft, draft-ietf-netconf-netconf-
              client-server-37, 14 August 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
              netconf-client-server-37>.

   [RESTCONF-CLIENT-SERVER]
              Watsen, K., "RESTCONF Client and Server Models", Work in
              Progress, Internet-Draft, draft-ietf-netconf-restconf-
              client-server-38, 14 August 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
              restconf-client-server-38>.

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

   [RFC5056]  Williams, N., "On the Use of Channel Bindings to Secure
              Channels", RFC 5056, DOI 10.17487/RFC5056, November 2007,
              <https://www.rfc-editor.org/info/rfc5056>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC8071]  Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
              RFC 8071, DOI 10.17487/RFC8071, February 2017,
              <https://www.rfc-editor.org/info/rfc8071>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/info/rfc8259>.

   [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>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [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>.

   [RFC8407BIS]
              Bierman, A., Boucadair, M., and Q. Wu, "Guidelines for
              Authors and Reviewers of Documents Containing YANG Data
              Models", Work in Progress, Internet-Draft, draft-ietf-
              netmod-rfc8407bis-17, 27 September 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
              rfc8407bis-17>.

   [RFC8996]  Moriarty, K. and S. Farrell, "Deprecating TLS 1.0 and TLS
              1.1", BCP 195, RFC 8996, DOI 10.17487/RFC8996, March 2021,
              <https://www.rfc-editor.org/info/rfc8996>.

   [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>.

   [RFC9257]  Housley, R., Hoyland, J., Sethi, M., and C. A. Wood,
              "Guidance for External Pre-Shared Key (PSK) Usage in TLS",
              RFC 9257, DOI 10.17487/RFC9257, July 2022,
              <https://www.rfc-editor.org/info/rfc9257>.

   [RFC9258]  Benjamin, D. and C. A. Wood, "Importing External Pre-
              Shared Keys (PSKs) for TLS 1.3", RFC 9258,
              DOI 10.17487/RFC9258, July 2022,
              <https://www.rfc-editor.org/info/rfc9258>.

   [RFC9643]  Watsen, K. and M. Scharf, "YANG Groupings for TCP Clients
              and TCP Servers", RFC 9643, DOI 10.17487/RFC9643, October
              2024, <https://www.rfc-editor.org/info/rfc9643>.

   [RFC9644]  Watsen, K., "YANG Groupings for SSH Clients and SSH
              Servers", RFC 9644, DOI 10.17487/RFC9644, October 2024,
              <https://www.rfc-editor.org/info/rfc9644>.

   [SYSTEM-CONFIG]
              Ma, Q., Wu, Q., and C. Feng, "System-defined
              Configuration", Work in Progress, Internet-Draft, draft-
              ietf-netmod-system-config-09, 29 September 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
              system-config-09>.

   [W3C.REC-xml-20081126]
              Bray, T., Paoli, J., Sperberg-McQueen, C. M., Maler, E.,
              and F. Yergeau, "Extensible Markup Language (XML) 1.0
              (Fifth Edition)", W3C Recommendation REC-xml-20081126,
              November 2008, <https://www.w3.org/TR/xml/>.

Appendix A.  Script to Generate IANA-Maintained YANG Modules

   This section is not normative.

   The Python <https://www.python.org> script contained in this section
   was used to create the initial IANA-maintained "iana-tls-cipher-
   suite-algs" YANG module maintained at [IANA-YANG-PARAMETERS].

   Run the script using the command 'python gen-yang-modules.py' to
   produce the YANG module file in the current directory.

   Be aware that the script does not attempt to copy the "revision"
   statements from the previous/current YANG module.  Copying the
   revision statements must be done manually.

   <CODE BEGINS>
   =============== NOTE: '\\' line wrapping per RFC 8792 ===============

   import re
   import csv
   import requests
   import textwrap
   import requests_cache
   from io import StringIO
   from datetime import datetime

   # Metadata for the one YANG module produced by this script
   MODULES = [
       {
           "csv_url": "https://www.iana.org/assignments/tls-parameters/\
   \tls-parameters-4.csv",
           "spaced_name": "cipher-suite",
           "hyphenated_name": "cipher-suite",
           "prefix": "tlscsa",
       }
   ]


   def create_module_begin(module, f):

       # Define template for all four modules
       PREAMBLE_TEMPLATE="""
   module iana-tls-HNAME-algs {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:iana-tls-HNAME-algs";
     prefix PREFIX;

     organization
       "Internet Assigned Numbers Authority (IANA)";

     contact
       "Postal: ICANN
                12025 Waterfront Drive, Suite 300
                Los Angeles, CA  90094-2536
                United States of America
        Tel:    +1 310 301 5800
        Email:  <iana@iana.org>";

     description
       "This module defines enumerations for the cipher suite
        algorithms defined in the 'TLS Cipher Suites' registry
        under the 'Transport Layer Security (TLS) Parameters'
        registry group maintained by IANA.

        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).

        The initial version of this YANG module is part of RFC 9645
        (https://www.rfc-editor.org/info/rfc9645); see the RFC
        itself for full legal notices.

        All versions of this module are published by IANA
        (https://www.iana.org/assignments/yang-parameters).";

     revision DATE {
       description
         "This initial version of the module was created using
          the script defined in RFC 9645 to reflect the contents
          of the SNAME algorithms registry maintained by IANA.";
       reference
         "RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
     }

     typedef tls-HNAME-algorithm {
       type enumeration {
   """
       # Replacements
       rep = {
         "DATE": datetime.today().strftime('%Y-%m-%d'),
         "YEAR": datetime.today().strftime('%Y'),
         "SNAME": module["spaced_name"],
         "HNAME": module["hyphenated_name"],
         "PREFIX": module["prefix"]
       }

       # Do the replacement
       rep = dict((re.escape(k), v) for k, v in rep.items())
       pattern = re.compile("|".join(rep.keys()))
       text = pattern.sub(lambda m: rep[re.escape(m.group(0))], PREAMBL\
   \E_TEMPLATE)

       # Write preamble into the file
       f.write(text)


   def create_module_body(module, f):

       # Fetch the current CSV file from IANA
       r = requests.get(module["csv_url"])
       assert r.status_code == 200, "Could not get " + module["csv_url"]

       # Parse each CSV line
       with StringIO(r.text) as csv_file:
           csv_reader = csv.DictReader(csv_file)
           for row in csv_reader:

               # Skip reserved algs
               if row["Description"].startswith("Unassigned"):
                   continue

               # Skip unassigned algs
               if row["Description"].startswith("Reserved"):
                   continue

               # Ensure this is the TLS line
               assert row["Description"].startswith("TLS_"), "Unrecogni\
   \zed description: '" + row["Description"] + "'"

               # Set the 'refs' and 'titles' lists
               if row["Reference"] == "":
                   pass # skip when the Reference field is empty

               else:

                   # There may be more than one ref
                   refs = row["Reference"][1:-1]  # remove the '[' and \
   \']' chars
                   refs = refs.split("][")
                   titles = []
                   for ref in refs:

                       # Ascertain the ref's title
                       if ref.startswith("RFC"):

                           # Fetch the current BIBTEX entry
                           bibtex_url="https://datatracker.ietf.org/doc\
   \/"+ ref.lower() + "/bibtex/"
                           r = requests.get(bibtex_url)
                           assert r.status_code == 200, "Could not GET \
   \" + bibtex_url

                           # Append to 'titles' value from the "title" \
   \line
                           for item in r.text.split("\n"):
                               if "title =" in item:
                                   title = re.sub('.*{{(.*)}}.*', r'\g<\
   \1>', item)
                                   if title.startswith("ECDHE\_PSK"):
                                       title = re.sub("ECDHE\\\\_PSK", \
   \"ECDHE_PSK", title)
                                   titles.append(re.sub('.*{{(.*)}}.*',\
   \ r'\g<1>', title))
                                   break
                           else:
                               raise Exception("RFC title not found")


                           # Insert a space: "RFC9645" --> "RFC 9645"
                           index = refs.index(ref)
                           refs[index] = "RFC " + ref[3:]

                       elif ref == "IESG Action 2018-08-16":

                           # Rewrite the ref value
                           index = refs.index(ref)
                           refs[index] = "IESG Action"

                           # Let title be something descriptive
                           titles.append("IESG Action 2018-08-16")

                       elif ref == "draft-irtf-cfrg-aegis-aead-08":

                           # Manually set the document's title
                           titles.append("The AEGIS Family of Authentic\
   \ated Encryption Algorithms")

                       elif ref:
                           raise Exception(f'ref "{ref}" not found')

                       else:
                           raise Exception(f'ref missing: {row}')

               # Write out the enum
               f.write(f'      enum {row["Description"]} {{\n');
               if row["Recommended"] == 'N':
                   f.write(f'        status deprecated;\n')
               f.write(f'        description\n')
               description = f'          "Enumeration for the \'{row["D\
   \escription"]}\' algorithm.";'
               description = textwrap.fill(description, width=69, subse\
   \quent_indent="           ")
               f.write(f'{description}\n')
               f.write('        reference\n')
               f.write('          "')
               if row["Reference"] == "":
                   f.write('Missing in IANA registry.')
               else:
                   ref_len = len(refs)
                   for i in range(ref_len):
                       ref = refs[i]
                       f.write(f'{ref}:\n')
                       title = "             " + titles[i]
                       if i == ref_len - 1:
                           title += '";'
                       title = textwrap.fill(title, width=69, subsequen\
   \t_indent="             ")
                       f.write(f'{title}')
                       if i != ref_len - 1:
                           f.write('\n           ')
               f.write('\n')
               f.write('      }\n')



   def create_module_end(module, f):

       # Close out the enumeration, typedef, and module
       f.write("    }\n")
       f.write("    description\n")
       f.write(f'      "An enumeration for TLS {module["spaced_name"]} \
   \algorithms.";\n')
       f.write("  }\n")
       f.write('\n')
       f.write('}\n')


   def create_module(module):

       # Install cache for 8x speedup
       requests_cache.install_cache()

       # Ascertain the yang module's name
       yang_module_name = "iana-tls-" + module["hyphenated_name"] + "-a\
   \lgs.yang"

       # Create yang module file
       with open(yang_module_name, "w") as f:
           create_module_begin(module, f)
           create_module_body(module, f)
           create_module_end(module, f)


   def main():
       for module in MODULES:
           create_module(module)


   if __name__ == "__main__":
       main()
   <CODE ENDS>

Acknowledgements

   The authors would like to thank the following for lively discussions
   on list and in the halls (ordered by first name): Alan Luchuk, Andy
   Bierman, Balázs Kovács, Benoit Claise, Bert Wijnen, David Lamparter,
   Dhruv Dhody, Éric Vyncke, Gary Wu, Henk Birkholz, Jeff Hartley,
   Jürgen Schönwälder, Ladislav Lhotka, Liang Xia, Martin Björklund,
   Martin Thomson, Mehmet Ersue, Michal Vaško, Murray Kucherawy, Paul
   Wouters, Phil Shafer, Qin Wu, Radek Krejci, Rob Wilton, Roman
   Danyliw, Russ Housley, Sean Turner, Thomas Martin, and Tom Petch.

Contributors

   Special acknowledgement goes to Gary Wu who contributed the "ietf-
   tls-common" module and Tom Petch who carefully ensured that
   references were set correctly throughout.

Author's Address

   Kent Watsen
   Watsen Networks
   Email: kent+ietf@watsen.net