Internet-Draft Groupings for TLS Clients and Servers May 2021
Watsen Expires 19 November 2021 [Page]
Workgroup:
NETCONF Working Group
Internet-Draft:
draft-ietf-netconf-tls-client-server-24
Published:
Intended Status:
Standards Track
Expires:
Author:
K. Watsen
Watsen Networks

YANG Groupings for TLS Clients and TLS Servers

Abstract

This document defines three YANG 1.1 modules: the first defines identities and groupings common to both TLS clients and TLS servers, the second defines a grouping for a generic TLS client, and the third defines a grouping for a generic TLS server.

Editorial Note (To be removed by RFC Editor)

This draft contains placeholder values that need to be replaced with finalized values at the time of publication. This note summarizes all of the substitutions that are needed. No other RFC Editor instructions are specified elsewhere in this document.

Artwork in this document contains shorthand references to drafts in progress. Please apply the following replacements:

  • AAAA --> the assigned RFC value for draft-ietf-netconf-crypto-types
  • BBBB --> the assigned RFC value for draft-ietf-netconf-trust-anchors
  • CCCC --> the assigned RFC value for draft-ietf-netconf-keystore
  • DDDD --> the assigned RFC value for draft-ietf-netconf-tcp-client-server
  • FFFF --> the assigned RFC value for this draft

Artwork in this document contains placeholder values for the date of publication of this draft. Please apply the following replacement:

  • 2021-05-18 --> the publication date of this draft

The following Appendix section is to be removed prior to publication:

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on 19 November 2021.

1. Introduction

This document defines three YANG 1.1 [RFC7950] modules: the first defines identities and groupings common to both TLS clients and TLS servers, the second defines a grouping for a generic TLS client, and the third defines a grouping for a generic TLS server. It is intended that these groupings will be used by applications using the TLS protocol [RFC5246]. For instance, these groupings could be used to help define the data model for an HTTPS [RFC2818] server or a NETCONF over TLS [RFC7589] based server.

The client and server YANG modules in this document each define one grouping, which is focused on just TLS-specific configuration, and specifically avoids 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 "ssh-server-grouping" grouping for the TLS parts it provides, while adding data nodes for the TCP-level call-home configuration.

1.1. Relation to other RFCs

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

The modules have been defined in a modular fashion to enable their use by other efforts, some of which are known to be in progress at the time of this writing, with many more expected to be defined in time.

The normative dependency relationship between the various RFCs in the collection is presented in the below diagram. The labels in the diagram represent the primary purpose provided by each RFC. Hyperlinks to each RFC are provided below the diagram.

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

Table 1: Label to RFC Mapping
Label in Diagram Originating RFC
crypto-types [I-D.ietf-netconf-crypto-types]
truststore [I-D.ietf-netconf-trust-anchors]
keystore [I-D.ietf-netconf-keystore]
tcp-client-server [I-D.ietf-netconf-tcp-client-server]
ssh-client-server [I-D.ietf-netconf-ssh-client-server]
tls-client-server [I-D.ietf-netconf-tls-client-server]
http-client-server [I-D.ietf-netconf-http-client-server]
netconf-client-server [I-D.ietf-netconf-netconf-client-server]
restconf-client-server [I-D.ietf-netconf-restconf-client-server]

1.2. 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.

1.3. Adherence to the NMDA

This document is compliant with the Network Management Datastore Architecture (NMDA) [RFC8342]. For instance, as described in [I-D.ietf-netconf-trust-anchors] and [I-D.ietf-netconf-keystore], trust anchors and keys installed during manufacturing are expected to appear in <operational>.

2. The "ietf-tls-common" Module

The TLS common model presented in this section contains identities 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 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 may serve to make TLS clients and TLS servers compliant with local security policies. This model supports both TLS1.2 [RFC5246] and TLS 1.3 [RFC8446].

TLS 1.2 and TLS 1.3 have different ways defining their own supported cryptographic algorithms, see TLS and DTLS IANA registries page (https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml):

  • TLS 1.2 defines four categories of registries for cryptographic algorithms: TLS Cipher Suites, TLS SignatureAlgorithm, TLS HashAlgorithm, TLS Supported Groups. TLS Cipher Suites plays the role of combining all of them into one set, as each value of the set represents a unique and feasible combination of all the cryptographic algorithms, and thus the other three registry categories do not need to be considered here. In this document, the TLS common model only chooses those TLS1.2 algorithms in TLS Cipher Suites which are marked as recommended: TLS_DHE_RSA_WITH_AES_128_GCM_SHA256, TLS_DHE_RSA_WITH_AES_256_GCM_SHA384, TLS_DHE_PSK_WITH_AES_128_GCM_SHA256, TLS_DHE_PSK_WITH_AES_256_GCM_SHA384, and so on. All chosen algorithms are enumerated in Table 1-1 below;
  • TLS 1.3 defines its supported algorithms differently. Firstly, it defines three categories of registries for cryptographic algorithms: TLS Cipher Suites, TLS SignatureScheme, TLS Supported Groups. Secondly, all three of these categories are useful, since they represent different parts of all the supported algorithms respectively. Thus, all of these registries categories are considered here. In this draft, the TLS common model chooses only those TLS1.3 algorithms specified in B.4, 4.2.3, 4.2.7 of [RFC8446].

Thus, in order to support both TLS1.2 and TLS1.3, the cipher-suites part of the "hello-params-grouping" grouping should include three parameters for configuring its permitted TLS algorithms, which are: TLS Cipher Suites, TLS SignatureScheme, TLS Supported Groups. Note that TLS1.2 only uses TLS Cipher Suites.

Features are defined for algorithms that are OPTIONAL or are not widely supported by popular implementations. Note that the list of algorithms is not exhaustive.

2.1. Data Model Overview

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

2.1.1. Features

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

Features:
  +-- tls-1_0
  +-- tls-1_1
  +-- tls-1_2
  +-- tls-1_3
  +-- tls-ecc
  +-- tls-dhe
  +-- tls-3des
  +-- tls-gcm
  +-- tls-sha2

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
  |  +-- tls-1.0
  |  +-- tls-1.1
  |  +-- tls-1.2
  |  +-- tls-1.3
  +-- cipher-suite-base
     +-- rsa-with-aes-128-cbc-sha
     +-- rsa-with-aes-256-cbc-sha
     +-- rsa-with-aes-128-cbc-sha256
     +-- rsa-with-aes-256-cbc-sha256
     +-- dhe-rsa-with-aes-128-cbc-sha
     +-- dhe-rsa-with-aes-256-cbc-sha
     +-- dhe-rsa-with-aes-128-cbc-sha256
     +-- dhe-rsa-with-aes-256-cbc-sha256
     +-- ecdhe-ecdsa-with-aes-128-cbc-sha256
     +-- ecdhe-ecdsa-with-aes-256-cbc-sha384
     +-- ecdhe-rsa-with-aes-128-cbc-sha256
     +-- ecdhe-rsa-with-aes-256-cbc-sha384
     +-- ecdhe-ecdsa-with-aes-128-gcm-sha256
     +-- ecdhe-ecdsa-with-aes-256-gcm-sha384
     +-- ecdhe-rsa-with-aes-128-gcm-sha256
     +-- ecdhe-rsa-with-aes-256-gcm-sha384
     +-- rsa-with-3des-ede-cbc-sha
     +-- ecdhe-rsa-with-3des-ede-cbc-sha
     +-- ecdhe-rsa-with-aes-128-cbc-sha
     +-- ecdhe-rsa-with-aes-256-cbc-sha

Comments:

  • The diagram shows that there are two base identities.
  • One base identity is used to specific TLS versions, while the other is used to specify cipher-suites.
  • These base identities are "abstract", in the object oriented programming sense, in that 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
    |  +-- tls-version*   identityref
    +-- cipher-suites
       +-- cipher-suite*   identityref

Comments:

  • This grouping is used by both the "tls-client-grouping" and the "tls-server-grouping" groupings defined in Section 3.1.2.1 and Section 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 "ietf-tls-common" module defines only "grouping" statements that are used by other modules to instantiate protocol-accessible nodes.

2.2. Example Usage

This section shows how it would appear if the "hello-params-grouping" grouping were 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>
    <tls-version>tlscmn:tls-1.1</tls-version>
    <tls-version>tlscmn:tls-1.2</tls-version>
  </tls-versions>
  <cipher-suites>
    <cipher-suite>tlscmn:dhe-rsa-with-aes-128-cbc-sha</cipher-suite>
    <cipher-suite>tlscmn:rsa-with-aes-128-cbc-sha</cipher-suite>
    <cipher-suite>tlscmn:rsa-with-3des-ede-cbc-sha</cipher-suite>
  </cipher-suites>
</hello-params>

2.3. YANG Module

This YANG module has a normative references to [RFC4346], [RFC5246], [RFC5288], [RFC5289], [RFC8422], and FIPS PUB 180-4.

This YANG module has a informative references to [RFC2246], [RFC4346], [RFC5246], and [RFC8446].

<CODE BEGINS> file "ietf-tls-common@2021-05-18.yang"

module ietf-tls-common {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-tls-common";
  prefix tlscmn;

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

  contact
    "WG Web:   <http://datatracker.ietf.org/wg/netconf/>
     WG List:  <mailto:netconf@ietf.org>
     Author:   Kent Watsen <mailto:kent+ietf@watsen.net>
     Author:   Gary Wu <mailto:garywu@cisco.com>";

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

     Copyright (c) 2021 IETF Trust and the persons identified
     as authors of the code. All rights reserved.

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

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

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
     'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
     'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
     are to be interpreted as described in BCP 14 (RFC 2119)
     (RFC 8174) when, and only when, they appear in all
     capitals, as shown here.";

  revision 2021-05-18 {
    description
      "Initial version";
    reference
      "RFC FFFF: YANG Groupings for TLS Clients and TLS Servers";
  }

  // Features

  feature tls-1_0 {
    description
      "TLS Protocol Version 1.0 is supported.  TLS 1.0 is obsolete
       and thus it is NOT RECOMMENDED to enable this feature.";
    reference
      "RFC 2246: The TLS Protocol Version 1.0";
  }

  feature tls-1_1 {
    description
      "TLS Protocol Version 1.1 is supported.  TLS 1.1 is obsolete
       and thus it is NOT RECOMMENDED to enable this feature.";
    reference
      "RFC 4346: The Transport Layer Security (TLS) Protocol
                 Version 1.1";
  }

  feature tls-1_2 {
    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 tls-1_3 {
    description
      "TLS Protocol Version 1.3 is supported.";
    reference
      "RFC 8446: The Transport Layer Security (TLS) Protocol
                 Version 1.3";
  }

  feature tls-ecc {
    description
      "Elliptic Curve Cryptography (ECC) is supported for TLS.";
    reference
      "RFC 8422: Elliptic Curve Cryptography (ECC) Cipher Suites
                 for Transport Layer Security (TLS)";
  }

  feature tls-dhe {
    description
      "Ephemeral Diffie-Hellman key exchange is supported for TLS.";
    reference
      "RFC 5246: The Transport Layer Security (TLS) Protocol
                 Version 1.2";
  }

  feature tls-3des {
    description
      "The Triple-DES block cipher is supported for TLS.";
    reference
      "RFC 5246: The Transport Layer Security (TLS) Protocol
                 Version 1.2";
  }

  feature tls-gcm {
    description
      "The Galois/Counter Mode authenticated encryption mode is
       supported for TLS.";
    reference
      "RFC 5288: AES Galois Counter Mode (GCM) Cipher Suites for
                 TLS";
  }

  feature tls-sha2 {
    description
      "The SHA2 family of cryptographic hash functions is supported
       for TLS.";
    reference
      "FIPS PUB 180-4: Secure Hash Standard (SHS)";
  }

  // Identities

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

  identity tls-1.0 {
    if-feature "tls-1_0";
    base tls-version-base;
    description
      "TLS Protocol Version 1.0.";
    reference
      "RFC 2246: The TLS Protocol Version 1.0";
  }

  identity tls-1.1 {
    if-feature "tls-1_1";
    base tls-version-base;
    description
      "TLS Protocol Version 1.1.";
    reference
      "RFC 4346: The Transport Layer Security (TLS) Protocol
                 Version 1.1";
  }

  identity tls-1.2 {
    if-feature "tls-1_2";
    base tls-version-base;
    description
      "TLS Protocol Version 1.2.";
    reference
      "RFC 5246: The Transport Layer Security (TLS) Protocol
                 Version 1.2";
  }

  identity tls-1.3 {
    if-feature "tls-1_3";
    base tls-version-base;
    description
      "TLS Protocol Version 1.3.";
    reference
      "RFC 8446: The Transport Layer Security (TLS) Protocol
                 Version 1.3";
  }

  identity cipher-suite-base {
    description
      "Base identity used to identify TLS cipher suites.";
  }

  identity rsa-with-aes-128-cbc-sha {
    base cipher-suite-base;
    description
      "Cipher suite TLS_RSA_WITH_AES_128_CBC_SHA.";
    reference
      "RFC 5246: The Transport Layer Security (TLS) Protocol
                 Version 1.2";
  }

  identity rsa-with-aes-256-cbc-sha {
    base cipher-suite-base;
    description
      "Cipher suite TLS_RSA_WITH_AES_256_CBC_SHA.";
    reference
      "RFC 5246: The Transport Layer Security (TLS) Protocol
                 Version 1.2";
  }

  identity rsa-with-aes-128-cbc-sha256 {
    if-feature "tls-sha2";
    base cipher-suite-base;
    description
      "Cipher suite TLS_RSA_WITH_AES_128_CBC_SHA256.";
    reference
      "RFC 5246: The Transport Layer Security (TLS) Protocol
                 Version 1.2";
  }

  identity rsa-with-aes-256-cbc-sha256 {
    if-feature "tls-sha2";
    base cipher-suite-base;
    description
      "Cipher suite TLS_RSA_WITH_AES_256_CBC_SHA256.";
    reference
      "RFC 5246: The Transport Layer Security (TLS) Protocol
                 Version 1.2";
  }

  identity dhe-rsa-with-aes-128-cbc-sha {
    if-feature "tls-dhe";
    base cipher-suite-base;
    description
      "Cipher suite TLS_DHE_RSA_WITH_AES_128_CBC_SHA.";
    reference
      "RFC 5246: The Transport Layer Security (TLS) Protocol
                 Version 1.2";
  }

  identity dhe-rsa-with-aes-256-cbc-sha {
    if-feature "tls-dhe";
    base cipher-suite-base;
    description
      "Cipher suite TLS_DHE_RSA_WITH_AES_256_CBC_SHA.";
    reference
      "RFC 5246: The Transport Layer Security (TLS) Protocol
                 Version 1.2";
  }

  identity dhe-rsa-with-aes-128-cbc-sha256 {
    if-feature "tls-dhe and tls-sha2";
    base cipher-suite-base;
    description
      "Cipher suite TLS_DHE_RSA_WITH_AES_128_CBC_SHA256.";
    reference
      "RFC 5246: The Transport Layer Security (TLS) Protocol
                 Version 1.2";
  }

  identity dhe-rsa-with-aes-256-cbc-sha256 {
    if-feature "tls-dhe and tls-sha2";
    base cipher-suite-base;
    description
      "Cipher suite TLS_DHE_RSA_WITH_AES_256_CBC_SHA256.";
    reference
      "RFC 5246: The Transport Layer Security (TLS) Protocol
                 Version 1.2";
  }

  identity ecdhe-ecdsa-with-aes-128-cbc-sha256 {
    if-feature "tls-ecc and tls-sha2";
    base cipher-suite-base;
    description
      "Cipher suite TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256.";
    reference
      "RFC 5289: TLS Elliptic Curve Cipher Suites with
                 SHA-256/384 and AES Galois Counter Mode (GCM)";
  }

  identity ecdhe-ecdsa-with-aes-256-cbc-sha384 {
    if-feature "tls-ecc and tls-sha2";
    base cipher-suite-base;
    description
      "Cipher suite TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384.";
    reference
      "RFC 5289: TLS Elliptic Curve Cipher Suites with
                 SHA-256/384 and AES Galois Counter Mode (GCM)";
  }

  identity ecdhe-rsa-with-aes-128-cbc-sha256 {
    if-feature "tls-ecc and tls-sha2";
    base cipher-suite-base;
    description
      "Cipher suite TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256.";
    reference
      "RFC 5289: TLS Elliptic Curve Cipher Suites with
                 SHA-256/384 and AES Galois Counter Mode (GCM)";
  }

  identity ecdhe-rsa-with-aes-256-cbc-sha384 {
    if-feature "tls-ecc and tls-sha2";
    base cipher-suite-base;
    description
      "Cipher suite TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384.";
    reference
      "RFC 5289: TLS Elliptic Curve Cipher Suites with
                 SHA-256/384 and AES Galois Counter Mode (GCM)";
  }

  identity ecdhe-ecdsa-with-aes-128-gcm-sha256 {
    if-feature "tls-ecc and tls-gcm and tls-sha2";
    base cipher-suite-base;
    description
      "Cipher suite TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256.";
    reference
      "RFC 5289: TLS Elliptic Curve Cipher Suites with
                 SHA-256/384 and AES Galois Counter Mode (GCM)";
  }

  identity ecdhe-ecdsa-with-aes-256-gcm-sha384 {
    if-feature "tls-ecc and tls-gcm and tls-sha2";
    base cipher-suite-base;
    description
      "Cipher suite TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384.";
    reference
      "RFC 5289: TLS Elliptic Curve Cipher Suites with
                 SHA-256/384 and AES Galois Counter Mode (GCM)";
  }

  identity ecdhe-rsa-with-aes-128-gcm-sha256 {
    if-feature "tls-ecc and tls-gcm and tls-sha2";
    base cipher-suite-base;
    description
      "Cipher suite TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256.";
    reference
      "RFC 5289: TLS Elliptic Curve Cipher Suites with
                 SHA-256/384 and AES Galois Counter Mode (GCM)";
  }

  identity ecdhe-rsa-with-aes-256-gcm-sha384 {
    if-feature "tls-ecc and tls-gcm and tls-sha2";
    base cipher-suite-base;
    description
      "Cipher suite TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384.";
    reference
      "RFC 5289: TLS Elliptic Curve Cipher Suites with
                 SHA-256/384 and AES Galois Counter Mode (GCM)";
  }

  identity rsa-with-3des-ede-cbc-sha {
    if-feature "tls-3des";
    base cipher-suite-base;
    description
      "Cipher suite TLS_RSA_WITH_3DES_EDE_CBC_SHA.";
    reference
      "RFC 5246: The Transport Layer Security (TLS) Protocol
                 Version 1.2";
  }

  identity ecdhe-rsa-with-3des-ede-cbc-sha {
    if-feature "tls-ecc and tls-3des";
    base cipher-suite-base;
    description
      "Cipher suite TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA.";
    reference
      "RFC 8422: Elliptic Curve Cryptography (ECC) Cipher Suites
                 for Transport Layer Security (TLS)";
  }

  identity ecdhe-rsa-with-aes-128-cbc-sha {
    if-feature "tls-ecc";
    base cipher-suite-base;
    description
      "Cipher suite TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA.";
    reference
      "RFC 8422: Elliptic Curve Cryptography (ECC) Cipher Suites
                 for Transport Layer Security (TLS)";
  }

  identity ecdhe-rsa-with-aes-256-cbc-sha {
    if-feature "tls-ecc";
    base cipher-suite-base;
    description
      "Cipher suite TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA.";
    reference
      "RFC 8422: Elliptic Curve Cryptography (ECC) Cipher Suites
                 for Transport Layer Security (TLS)";
  }

  // 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";
    container tls-versions {
      description
        "Parameters regarding TLS versions.";
      leaf-list tls-version {
        type identityref {
          base tls-version-base;
        }
        description
          "Acceptable TLS protocol versions.

           If this leaf-list is not configured (has zero elements)
           the acceptable TLS protocol versions are implementation-
           defined.";
      }
    }
    container cipher-suites {
      description
        "Parameters regarding cipher suites.";
      leaf-list cipher-suite {
        type identityref {
          base cipher-suite-base;
        }
        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 FFFF for
           valid combinations.

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

}

<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 Examples (Section 3.2). 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-hello-params-config
  +-- 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

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:local-or-keystore-end-entity-cert-with-key-\
grouping
    |     +--:(raw-public-key) {client-ident-raw-public-key}?
    |     |  +-- raw-private-key
    |     |     +---u ks:local-or-keystore-asymmetric-key-grouping
    |     +--:(psk) {client-ident-psk}?
    |        +-- psk
    |           +---u ks:local-or-keystore-symmetric-key-grouping
    |           +-- id?
    |                   string
    +-- server-authentication
    |  +-- ca-certs! {client-ident-x509-cert}?
    |  |  +---u ts:local-or-truststore-certs-grouping
    |  +-- ee-certs! {client-ident-x509-cert}?
    |  |  +---u ts:local-or-truststore-certs-grouping
    |  +-- raw-public-keys! {client-ident-raw-public-key}?
    |  |  +---u ts:local-or-truststore-public-keys-grouping
    |  +-- psks?              empty {client-ident-psk}?
    +-- hello-params {tls-client-hello-params-config}?
    |  +---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 for testing the aliveness of the TLS server. The aliveness-test occurs at the TLS protocol layer.
  • For the referenced grouping statement(s):

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.

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 of [I-D.ietf-netconf-trust-anchors] and Section 3.2 of [I-D.ietf-netconf-keystore].

The following configuration example uses local-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>
      <local-definition>
        <public-key-format>ct:subject-public-key-info-format</public\
-key-format>
        <public-key>base64encodedvalue==</public-key>
        <private-key-format>ct:rsa-private-key-format</private-key-f\
ormat>
        <cleartext-private-key>base64encodedvalue==</cleartext-priva\
te-key>
        <cert-data>base64encodedvalue==</cert-data>
      </local-definition>
    </certificate>
    <!-- TESTED, BUT COMMENTED OUT DUE TO ONLY ONE ALLOWED AT A TIME
    <raw-private-key>
      <local-definition>
        <public-key-format>ct:subject-public-key-info-format</public\
-key-format>
        <public-key>base64encodedvalue==</public-key>
        <private-key-format>ct:rsa-private-key-format</private-key-f\
ormat>
        <cleartext-private-key>base64encodedvalue==</cleartext-priva\
te-key>
      </local-definition>
    </raw-private-key>
    <psk>
      <local-definition>
        <key-format>ct:octet-string-key-format</key-format>
        <cleartext-key>base64encodedvalue==</cleartext-key>
      </local-definition>
    </psk>
    -->
  </client-identity>

  <!-- which certificates will this client trust -->
  <server-authentication>
    <ca-certs>
      <local-definition>
        <certificate>
          <name>Server Cert Issuer #1</name>
          <cert-data>base64encodedvalue==</cert-data>
        </certificate>
        <certificate>
          <name>Server Cert Issuer #2</name>
          <cert-data>base64encodedvalue==</cert-data>
        </certificate>
      </local-definition>
    </ca-certs>
    <ee-certs>
      <local-definition>
        <certificate>
          <name>My Application #1</name>
          <cert-data>base64encodedvalue==</cert-data>
        </certificate>
        <certificate>
          <name>My Application #2</name>
          <cert-data>base64encodedvalue==</cert-data>
        </certificate>
      </local-definition>
    </ee-certs>
    <raw-public-keys>
      <local-definition>
        <public-key>
          <name>corp-fw1</name>
          <public-key-format>ct:subject-public-key-info-format</publ\
ic-key-format>
          <public-key>base64encodedvalue==</public-key>
        </public-key>
        <public-key>
          <name>corp-fw1</name>
          <public-key-format>ct:subject-public-key-info-format</publ\
ic-key-format>
          <public-key>base64encodedvalue==</public-key>
        </public-key>
      </local-definition>
    </raw-public-keys>
    <psks/>
  </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 keystore-references for the client identity and 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>
      <keystore-reference>
        <asymmetric-key>rsa-asymmetric-key</asymmetric-key>
        <certificate>ex-rsa-cert</certificate>
      </keystore-reference>
    </certificate>
    <!-- TESTED, BUT COMMENTED OUT DUE TO ONLY ONE ALLOWED AT A TIME
    <raw-private-key>
      <keystore-reference>raw-private-key</keystore-reference>
    </raw-private-key>
    <psk>
      <keystore-reference>encrypted-symmetric-key</keystore-referenc\
e>
    </psk>
    -->
  </client-identity>

  <!-- which certificates will this client trust -->
  <server-authentication>
    <ca-certs>
      <truststore-reference>trusted-server-ca-certs</truststore-refe\
rence>
    </ca-certs>
    <ee-certs>
      <truststore-reference>trusted-server-ee-certs</truststore-refe\
rence>
    </ee-certs>
    <raw-public-keys>
      <truststore-reference>Raw Public Keys for TLS Servers</trustst\
ore-reference>
    </raw-public-keys>
    <psks/>
  </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 [I-D.ietf-netconf-trust-anchors] and [I-D.ietf-netconf-keystore].

<CODE BEGINS> file "ietf-tls-client@2021-05-18.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 AAAA: YANG Data Types and Groupings for Cryptography";
  }

  import ietf-truststore {
    prefix ts;
    reference
      "RFC BBBB: A YANG Data Model for a Truststore";
  }

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

  import ietf-tls-common {
    prefix tlscmn;
    revision-date 2021-05-18; // stable grouping definitions
    reference
      "RFC FFFF: YANG Groupings for TLS Clients and TLS Servers";
  }

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

  contact
    "WG Web:   <http://datatracker.ietf.org/wg/netconf/>
     WG List:  <mailto:netconf@ietf.org>
     Author:   Kent Watsen <mailto:kent+ietf@watsen.net>
     Author:   Gary Wu <mailto:garywu@cisco.com>";

  description
    "This module defines reusable groupings for TLS clients that
     can be used as a basis for specific TLS client instances.

     Copyright (c) 2021 IETF Trust and the persons identified
     as authors of the code. All rights reserved.

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

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

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
     'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
     'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
     are to be interpreted as described in BCP 14 (RFC 2119)
     (RFC 8174) when, and only when, they appear in all
     capitals, as shown here.";

  revision 2021-05-18 {
    description
      "Initial version";
    reference
      "RFC FFFF: YANG Groupings for TLS Clients and TLS Servers";
  }

  // Features

  feature tls-client-hello-params-config {
    description
      "TLS hello message parameters are configurable on a TLS
       client.";
  }

  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.";
  }

  feature client-ident-raw-public-key {
    description
      "Indicates that the client supports identifying itself
       using raw public keys.";
  }

  feature client-ident-psk {
    description
      "Indicates that the client supports identifying itself
       using PSKs (pre-shared or pairwise-symmetric keys).";
  }

  feature server-auth-x509-cert {
    description
      "Indicates that the client supports authenticating servers
       using X.509 certificates.";
  }

  feature server-auth-raw-public-key {
    description
      "Indicates that the client supports authenticating servers
       using raw public keys.";
  }

  feature server-auth-psk {
    description
      "Indicates that the client supports authenticating servers
       using PSKs (pre-shared or pairwise-symmetric keys).";
  }

  // 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 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 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.";
      reference
        "RFC 5246: The Transport Layer Security (TLS) Protocol
                   Version 1.2
         RFC CCCC: A YANG Data Model for a Keystore";
      choice auth-type {
        mandatory true;
        description
          "A choice amongst available authentication types.";
        case certificate {
          if-feature "client-ident-x509-cert";
          container certificate {
            description
              "Specifies the client identity using a certificate.";
            uses
              ks:local-or-keystore-end-entity-cert-with-key-grouping{
              refine "local-or-keystore/local/local-definition" {
                must 'public-key-format'
                   + ' = "ct:subject-public-key-info-format"';
              }
              refine "local-or-keystore/keystore/keystore-reference"
                   + "/asymmetric-key" {
                must '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:local-or-keystore-asymmetric-key-grouping {
              refine "local-or-keystore/local/local-definition" {
                must 'public-key-format'
                   + ' = "ct:subject-public-key-info-format"';
              }
              refine "local-or-keystore/keystore"
                   + "/keystore-reference" {
                must 'deref(.)/../ks:public-key-format'
                   + ' = "ct:subject-public-key-info-format"';
              }
            }
          }
        }
        case psk {
          if-feature "client-ident-psk";
          container psk {
            description
              "Specifies the client identity using a PSK (pre-shared
               or pairwise-symmetric key).";
            uses ks:local-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)";
            }
          }
        }
      }
    } // container client-identity

    container server-authentication {
      nacm:default-deny-write;
      must 'ca-certs or ee-certs or raw-public-keys or psks';
      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 PSK (pre-shared
         or pairwise-symmetric key) based authentication as the key
         is necessarily the same as configured in the '../client-
         identity' node.";
      container ca-certs {
        if-feature "client-ident-x509-cert";
        presence
          "Indicates that 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 certificate authority (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 BBBB: A YANG Data Model for a Truststore";
        uses ts:local-or-truststore-certs-grouping;
      }
      container ee-certs {
        if-feature "client-ident-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 server certificates (i.e., end entity
           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 BBBB: A YANG Data Model for a Truststore";
        uses ts:local-or-truststore-certs-grouping;
      }
      container raw-public-keys {
        if-feature "client-ident-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 BBBB: A YANG Data Model for a Truststore";
        uses ts:local-or-truststore-public-keys-grouping {
          refine "local-or-truststore/local/local-definition"
               + "/public-key" {
            must 'public-key-format'
               + ' = "ct:subject-public-key-info-format"';
          }
          refine "local-or-truststore/truststore"
               + "/truststore-reference" {
            must 'deref(.)/../*/ts:public-key-format'
               + ' = "ct:subject-public-key-info-format"';
          }
        }
      }
      leaf psks {
        if-feature "client-ident-psk";
        type empty;
        description
          "Indicates that the TLS client can authenticate TLS servers
           using configure PSKs (pre-shared or pairwise-symmetric
           keys).

           No configuration is required since the PSK value is the
           same as PSK value configured in the 'client-identity'
           node.";
      }
    } // container server-authentication

    container hello-params {
      nacm:default-deny-write;
      if-feature "tls-client-hello-params-config";
      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 keep-alive 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 by 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 if
             no data has been received from the TLS server, a
             TLS-level message will be sent to test the
             aliveness of the TLS server.";
        }
        leaf max-attempts {
          type uint8;
          default "3";
          description
            "Sets the maximum number of sequential keep-alive
             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 Examples (Section 4.2). 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-hello-params-config
  +-- 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

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:local-or-keystore-end-entity-cert-with-key-\
grouping
    |     +--:(raw-private-key) {server-ident-raw-public-key}?
    |     |  +-- raw-private-key
    |     |     +---u ks:local-or-keystore-asymmetric-key-grouping
    |     +--:(psk) {server-ident-psk}?
    |        +-- psk
    |           +---u ks:local-or-keystore-symmetric-key-grouping
    |           +-- id_hint?
    |                   string
    +-- client-authentication! {client-auth-supported}?
    |  +-- ca-certs! {client-auth-x509-cert}?
    |  |  +---u ts:local-or-truststore-certs-grouping
    |  +-- ee-certs! {client-auth-x509-cert}?
    |  |  +---u ts:local-or-truststore-certs-grouping
    |  +-- raw-public-keys! {client-auth-raw-public-key}?
    |  |  +---u ts:local-or-truststore-public-keys-grouping
    |  +-- psks?              empty {client-auth-psk}?
    +-- hello-params {tls-server-hello-params-config}?
    |  +---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 for testing the aliveness of the TLSi client. The aliveness-tests occurs at the TLS protocol layer.
  • For the referenced grouping statement(s):

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.

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 of [I-D.ietf-netconf-trust-anchors] and Section 3.2 of [I-D.ietf-netconf-keystore].

The following configuration example uses local-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>
      <local-definition>
        <public-key-format>ct:subject-public-key-info-format</public\
-key-format>
        <public-key>base64encodedvalue==</public-key>
        <private-key-format>ct:rsa-private-key-format</private-key-f\
ormat>
        <cleartext-private-key>base64encodedvalue==</cleartext-priva\
te-key>
        <cert-data>base64encodedvalue==</cert-data>
      </local-definition>
    </certificate>
    <!-- TESTED, BUT COMMENTED OUT DUE TO ONLY ONE ALLOWED AT A TIME
    <raw-private-key>
      <local-definition>
        <public-key-format>ct:subject-public-key-info-format</public\
-key-format>
        <public-key>base64encodedvalue==</public-key>
        <private-key-format>ct:rsa-private-key-format</private-key-f\
ormat>
        <cleartext-private-key>base64encodedvalue==</cleartext-priva\
te-key>
      </local-definition>
    </raw-private-key>
    <psk>
      <local-definition>
        <key-format>ct:octet-string-key-format</key-format>
        <cleartext-key>base64encodedvalue==</cleartext-key>
      </local-definition>
    </psk>
    -->
  </server-identity>

  <!-- which certificates will this server trust -->
  <client-authentication>
    <ca-certs>
      <local-definition>
        <certificate>
          <name>Identity Cert Issuer #1</name>
          <cert-data>base64encodedvalue==</cert-data>
        </certificate>
        <certificate>
          <name>Identity Cert Issuer #2</name>
          <cert-data>base64encodedvalue==</cert-data>
        </certificate>
      </local-definition>
    </ca-certs>
    <ee-certs>
      <local-definition>
        <certificate>
          <name>Application #1</name>
          <cert-data>base64encodedvalue==</cert-data>
        </certificate>
        <certificate>
          <name>Application #2</name>
          <cert-data>base64encodedvalue==</cert-data>
        </certificate>
      </local-definition>
    </ee-certs>
    <raw-public-keys>
      <local-definition>
        <public-key>
          <name>User A</name>
          <public-key-format>ct:subject-public-key-info-format</publ\
ic-key-format>
          <public-key>base64encodedvalue==</public-key>
        </public-key>
        <public-key>
          <name>User B</name>
          <public-key-format>ct:subject-public-key-info-format</publ\
ic-key-format>
          <public-key>base64encodedvalue==</public-key>
        </public-key>
      </local-definition>
    </raw-public-keys>
    <psks/>
  </client-authentication>

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

</tls-server>

The following configuration example uses keystore-references for the server identity and 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>
      <keystore-reference>
        <asymmetric-key>rsa-asymmetric-key</asymmetric-key>
        <certificate>ex-rsa-cert</certificate>
      </keystore-reference>
    </certificate>
    <!-- TESTED, BUT COMMENTED OUT DUE TO ONLY ONE ALLOWED AT A TIME
    <raw-private-key>
      <keystore-reference>raw-private-key</keystore-reference>
    </raw-private-key>
    <psk>
      <keystore-reference>encrypted-symmetric-key</keystore-referenc\
e>
    </psk>
    -->
  </server-identity>

  <!-- which certificates will this server trust -->
  <client-authentication>
    <ca-certs>
      <truststore-reference>trusted-client-ca-certs</truststore-refe\
rence>
    </ca-certs>
    <ee-certs>
      <truststore-reference>trusted-client-ee-certs</truststore-refe\
rence>
    </ee-certs>
    <raw-public-keys>
      <truststore-reference>Raw Public Keys for TLS Clients</trustst\
ore-reference>
    </raw-public-keys>
    <psks/>
  </client-authentication>

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

</tls-server>

4.3. YANG Module

This YANG module has a normative references to [RFC5246], [I-D.ietf-netconf-trust-anchors] and [I-D.ietf-netconf-keystore].

<CODE BEGINS> file "ietf-tls-server@2021-05-18.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 AAAA: YANG Data Types and Groupings for Cryptography";
  }

  import ietf-truststore {
    prefix ts;
    reference
      "RFC BBBB: A YANG Data Model for a Truststore";
  }

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

  import ietf-tls-common {
    prefix tlscmn;
    revision-date 2021-05-18; // stable grouping definitions
    reference
      "RFC FFFF: YANG Groupings for TLS Clients and TLS Servers";
  }

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

  contact
    "WG Web:   <http://datatracker.ietf.org/wg/netconf/>
     WG List:  <mailto:netconf@ietf.org>
     Author:   Kent Watsen <mailto:kent+ietf@watsen.net>
     Author:   Gary Wu <mailto:garywu@cisco.com>";

  description
    "This module defines reusable groupings for TLS servers that
     can be used as a basis for specific TLS server instances.

     Copyright (c) 2021 IETF Trust and the persons identified
     as authors of the code. All rights reserved.

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

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

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
     'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
     'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
     are to be interpreted as described in BCP 14 (RFC 2119)
     (RFC 8174) when, and only when, they appear in all
     capitals, as shown here.";

  revision 2021-05-18 {
    description
      "Initial version";
    reference
      "RFC FFFF: YANG Groupings for TLS Clients and TLS Servers";
  }

  // Features

  feature tls-server-hello-params-config {
    description
      "TLS hello message parameters are configurable on a TLS
       server.";
  }

  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.";
  }

  feature server-ident-raw-public-key {
    description
      "Indicates that the server supports identifying itself
       using raw public keys.";
  }

  feature server-ident-psk {
    description
      "Indicates that the server supports identifying itself
       using PSKs (pre-shared or pairwise-symmetric keys).";
  }

  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.";
  }

  feature client-auth-raw-public-key {
    description
      "Indicates that the server supports authenticating clients
       using raw public keys.";
  }

  feature client-auth-psk {
    description
      "Indicates that the server supports authenticating clients
       using PSKs (pre-shared or pairwise-symmetric keys).";
  }

  // 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 certificate,
         including any configured intermediate certificates, the
         TLS server will present when establishing a TLS connection
         in its Certificate message, as defined in Section 7.4.2
         in RFC 5246.";
      reference
        "RFC 5246: The Transport Layer Security (TLS) Protocol
                   Version 1.2
         RFC CCCC: A YANG Data Model for a Keystore";
      choice auth-type {
        mandatory true;
        description
          "A choice amongst authentication types.";
        case certificate {
          if-feature "server-ident-x509-cert";
          container certificate {
            description
              "Specifies the server identity using a certificate.";
            uses
              ks:local-or-keystore-end-entity-cert-with-key-grouping{
              refine "local-or-keystore/local/local-definition" {
                must 'public-key-format'
                   + ' = "ct:subject-public-key-info-format"';
              }
              refine "local-or-keystore/keystore/keystore-reference"
                   + "/asymmetric-key" {
                must '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:local-or-keystore-asymmetric-key-grouping {
              refine "local-or-keystore/local/local-definition" {
                must 'public-key-format'
                   + ' = "ct:subject-public-key-info-format"';
              }
              refine "local-or-keystore/keystore/keystore-reference"{
                must 'deref(.)/../ks:public-key-format'
                   + ' = "ct:subject-public-key-info-format"';
              }
            }
          }
        }
        case psk {
          if-feature "server-ident-psk";
          container psk {
            description
              "Specifies the server identity using a PSK (pre-shared
               or pairwise-symmetric key).";
            uses ks:local-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)";
            }
          }
        }
      }
    } // 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 psks';
      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 the
         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 PSK (pre-shared
         or pairwise-symmetric key) based authentication as 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 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 certificate authority (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 BBBB: A YANG Data Model for a Truststore";
        uses ts:local-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., end entity
           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 BBBB: A YANG Data Model for a Truststore";
        uses ts:local-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 BBBB: A YANG Data Model for a Truststore";
        uses ts:local-or-truststore-public-keys-grouping {
          refine "local-or-truststore/local/local-definition"
               + "/public-key" {
            must 'public-key-format'
               + ' = "ct:subject-public-key-info-format"';
          }
          refine "local-or-truststore/truststore"
               + "/truststore-reference" {
            must 'deref(.)/../*/ts:public-key-format'
               + ' = "ct:subject-public-key-info-format"';
          }
        }
      }
      leaf psks {
        if-feature "client-auth-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.";
      }
    } // container client-authentication

    container hello-params {
      nacm:default-deny-write;
      if-feature "tls-server-hello-params-config";
      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 keep-alive 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 if
             no data has been received from the TLS client, a
             TLS-level message will be sent to test the
             aliveness of the TLS client.";
        }
        leaf max-attempts {
          type uint8;
          default "3";
          description
            "Sets the maximum number of sequential keep-alive
             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

5.1. The "ietf-tls-common" YANG Module

The "ietf-tls-common" YANG module defines "grouping" statements that are designed to be accessed via YANG based management protocols, such as NETCONF [RFC6241] and RESTCONF [RFC8040]. Both of these protocols have mandatory-to-implement secure transport layers (e.g., SSH, TLS) with mutual authentication.

The NETCONF access control model (NACM) [RFC8341] provides the means to restrict access for particular users to a pre-configured subset of all available protocol operations and content.

Since the module in this document only define groupings, these considerations are primarily for the designers of other modules that use these groupings.

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 does not define any RPCs, actions, or notifications, and thus the security consideration for such is not provided here.

5.2. The "ietf-tls-client" YANG Module

The "ietf-tls-client" YANG module defines "grouping" statements that are designed to be accessed via YANG based management protocols, such as NETCONF [RFC6241] and RESTCONF [RFC8040]. Both of these protocols have mandatory-to-implement secure transport layers (e.g., SSH, TLS) with mutual authentication.

The NETCONF access control model (NACM) [RFC8341] provides the means to restrict access for particular users to a pre-configured subset of all available protocol operations and content.

Since the module in this document only define groupings, these considerations are primarily for the designers of other modules that use these groupings.

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 of 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 consideration for such is not provided here.

5.3. The "ietf-tls-server" YANG Module

The "ietf-tls-server" YANG module defines "grouping" statements that are designed to be accessed via YANG based management protocols, such as NETCONF [RFC6241] and RESTCONF [RFC8040]. Both of these protocols have mandatory-to-implement secure transport layers (e.g., SSH, TLS) with mutual authentication.

The NETCONF access control model (NACM) [RFC8341] provides the means to restrict access for particular users to a pre-configured subset of all available protocol operations and content.

Since the module in this document only define groupings, these considerations are primarily for the designers of other modules that use these groupings.

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 of 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 consideration for such is not provided here.

6. IANA Considerations

6.1. The "IETF XML" Registry

This document registers three URIs in the "ns" subregistry of the IETF XML Registry [RFC3688]. Following the format in [RFC3688], the following registrations are requested:

   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

This document registers three YANG modules in the YANG Module Names registry [RFC6020]. Following the format in [RFC6020], the following registrations are requested:

   name:         ietf-tls-common
   namespace:    urn:ietf:params:xml:ns:yang:ietf-tls-common
   prefix:       tlscmn
   reference:    RFC FFFF

   name:         ietf-tls-client
   namespace:    urn:ietf:params:xml:ns:yang:ietf-tls-client
   prefix:       tlsc
   reference:    RFC FFFF

   name:         ietf-tls-server
   namespace:    urn:ietf:params:xml:ns:yang:ietf-tls-server
   prefix:       tlss
   reference:    RFC FFFF

7. References

7.1. Normative References

[I-D.ietf-netconf-crypto-types]
Watsen, K., "YANG Data Types and Groupings for Cryptography", Work in Progress, Internet-Draft, draft-ietf-netconf-crypto-types-19, , <https://tools.ietf.org/html/draft-ietf-netconf-crypto-types-19>.
[I-D.ietf-netconf-keystore]
Watsen, K., "A YANG Data Model for a Keystore", Work in Progress, Internet-Draft, draft-ietf-netconf-keystore-21, , <https://tools.ietf.org/html/draft-ietf-netconf-keystore-21>.
[I-D.ietf-netconf-trust-anchors]
Watsen, K., "A YANG Data Model for a Truststore", Work in Progress, Internet-Draft, draft-ietf-netconf-trust-anchors-14, , <https://tools.ietf.org/html/draft-ietf-netconf-trust-anchors-14>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC5288]
Salowey, J., Choudhury, A., and D. McGrew, "AES Galois Counter Mode (GCM) Cipher Suites for TLS", RFC 5288, DOI 10.17487/RFC5288, , <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, , <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, , <https://www.rfc-editor.org/info/rfc6020>.
[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, , <https://www.rfc-editor.org/info/rfc7589>.
[RFC7950]
Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, , <https://www.rfc-editor.org/info/rfc7950>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <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, , <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, , <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, , <https://www.rfc-editor.org/info/rfc8446>.

7.2. Informative References

[I-D.ietf-netconf-http-client-server]
Watsen, K., "YANG Groupings for HTTP Clients and HTTP Servers", Work in Progress, Internet-Draft, draft-ietf-netconf-http-client-server-06, , <https://tools.ietf.org/html/draft-ietf-netconf-http-client-server-06>.
[I-D.ietf-netconf-netconf-client-server]
Watsen, K., "NETCONF Client and Server Models", Work in Progress, Internet-Draft, draft-ietf-netconf-netconf-client-server-22, , <https://tools.ietf.org/html/draft-ietf-netconf-netconf-client-server-22>.
[I-D.ietf-netconf-restconf-client-server]
Watsen, K., "RESTCONF Client and Server Models", Work in Progress, Internet-Draft, draft-ietf-netconf-restconf-client-server-22, , <https://tools.ietf.org/html/draft-ietf-netconf-restconf-client-server-22>.
[I-D.ietf-netconf-ssh-client-server]
Watsen, K., "YANG Groupings for SSH Clients and SSH Servers", Work in Progress, Internet-Draft, draft-ietf-netconf-ssh-client-server-23, , <https://tools.ietf.org/html/draft-ietf-netconf-ssh-client-server-23>.
[I-D.ietf-netconf-tcp-client-server]
Watsen, K. and M. Scharf, "YANG Groupings for TCP Clients and TCP Servers", Work in Progress, Internet-Draft, draft-ietf-netconf-tcp-client-server-09, , <https://tools.ietf.org/html/draft-ietf-netconf-tcp-client-server-09>.
[I-D.ietf-netconf-tls-client-server]
Watsen, K., "YANG Groupings for TLS Clients and TLS Servers", Work in Progress, Internet-Draft, draft-ietf-netconf-tls-client-server-23, , <https://tools.ietf.org/html/draft-ietf-netconf-tls-client-server-23>.
[RFC2246]
Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 2246, DOI 10.17487/RFC2246, , <https://www.rfc-editor.org/info/rfc2246>.
[RFC2818]
Rescorla, E., "HTTP Over TLS", RFC 2818, DOI 10.17487/RFC2818, , <https://www.rfc-editor.org/info/rfc2818>.
[RFC3688]
Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, , <https://www.rfc-editor.org/info/rfc3688>.
[RFC4346]
Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, DOI 10.17487/RFC4346, , <https://www.rfc-editor.org/info/rfc4346>.
[RFC5246]
Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, , <https://www.rfc-editor.org/info/rfc5246>.
[RFC6241]
Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, , <https://www.rfc-editor.org/info/rfc6241>.
[RFC8040]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, , <https://www.rfc-editor.org/info/rfc8040>.
[RFC8071]
Watsen, K., "NETCONF Call Home and RESTCONF Call Home", RFC 8071, DOI 10.17487/RFC8071, , <https://www.rfc-editor.org/info/rfc8071>.
[RFC8340]
Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, , <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, , <https://www.rfc-editor.org/info/rfc8342>.

Appendix A. Change Log

This section is to be removed before publishing as an RFC.

A.1. 00 to 01

  • Noted that '0.0.0.0' and '::' might have special meanings.
  • Renamed "keychain" to "keystore".

A.2. 01 to 02

  • Removed the groupings containing transport-level configuration. Now modules contain only the transport-independent groupings.
  • Filled in previously incomplete 'ietf-tls-client' module.
  • Added cipher suites for various algorithms into new 'ietf-tls-common' module.

A.3. 02 to 03

  • Added a 'must' statement to container 'server-auth' asserting that at least one of the various auth mechanisms must be specified.
  • Fixed description statement for leaf 'trusted-ca-certs'.

A.4. 03 to 04

  • Updated title to "YANG Groupings for TLS Clients and TLS Servers"
  • Updated leafref paths to point to new keystore path
  • Changed the YANG prefix for ietf-tls-common from 'tlscom' to 'tlscmn'.
  • Added TLS protocol verions 1.0 and 1.1.
  • Made author lists consistent
  • Now tree diagrams reference ietf-netmod-yang-tree-diagrams
  • Updated YANG to use typedefs around leafrefs to common keystore paths
  • Now inlines key and certificates (no longer a leafref to keystore)

A.5. 04 to 05

  • Merged changes from co-author.

A.6. 05 to 06

  • Updated to use trust anchors from trust-anchors draft (was keystore draft)
  • Now Uses new keystore grouping enabling asymmetric key to be either locally defined or a reference to the keystore.

A.7. 06 to 07

  • factored the tls-[client|server]-groupings into more reusable groupings.
  • added if-feature statements for the new "x509-certificates" feature defined in draft-ietf-netconf-trust-anchors.

A.8. 07 to 08

  • Added a number of compatibility matrices to Section 5 (thanks Frank!)
  • Clarified that any configured "cipher-suite" values need to be compatible with the configured private key.

A.9. 08 to 09

  • Updated examples to reflect update to groupings defined in the keystore draft.
  • Add TLS keepalives features and groupings.
  • Prefixed top-level TLS grouping nodes with 'tls-' and support mashups.
  • Updated copyright date, boilerplate template, affiliation, and folding algorithm.

A.10. 09 to 10

  • Reformatted the YANG modules.

A.11. 10 to 11

  • Collapsed all the inner groupings into the top-level grouping.
  • Added a top-level "demux container" inside the top-level grouping.
  • Added NACM statements and updated the Security Considerations section.
  • Added "presence" statements on the "keepalive" containers, as was needed to address a validation error that appeared after adding the "must" statements into the NETCONF/RESTCONF client/server modules.
  • Updated the boilerplate text in module-level "description" statement to match copyeditor convention.

A.12. 11 to 12

  • In server model, made 'client-authentication' a 'presence' node indicating that the server supports client authentication.
  • In the server model, added a 'required-or-optional' choice to 'client-authentication' to better support protocols such as RESTCONF.
  • In the server model, added a 'local-or-external' choice to 'client-authentication' to better support consuming data models that prefer to keep client auth with client definitions than in a model principally concerned with the "transport".
  • In both models, removed the "demux containers", floating the nacm:default-deny-write to each descendent node, and adding a note to model designers regarding the potential need to add their own demux containers.
  • Fixed a couple references (section 2 --> section 3)

A.13. 12 to 13

  • Updated to reflect changes in trust-anchors drafts (e.g., s/trust-anchors/truststore/g + s/pinned.//)

A.14. 12 to 13

  • Removed 'container' under 'client-identity' to match server model.
  • Updated examples to reflect change grouping in keystore module.

A.15. 13 to 14

  • Removed the "certificate" container from "client-identity" in the ietf-tls-client module.
  • Updated examples to reflect ietf-crypto-types change (e.g., identities --> enumerations)

A.16. 14 to 15

  • Updated "server-authentication" and "client-authentication" nodes from being a leaf of type "ts:certificates-ref" to a container that uses "ts:local-or-truststore-certs-grouping".

A.17. 15 to 16

  • Removed unnecessary if-feature statements in the -client and -server modules.
  • Cleaned up some description statements in the -client and -server modules.
  • Fixed a canonical ordering issue in ietf-tls-common detected by new pyang.

A.18. 16 to 17

  • Removed choice local-or-external by removing the 'external' case and flattening the 'local' case and adding a "client-auth-supported" feature.
  • Removed choice required-or-optional.
  • Updated examples to include the "*-key-format" nodes.
  • Augmented-in "must" expressions ensuring that locally-defined public-key-format are "ct:ssh-public-key-format" (must expr for ref'ed keys are TBD).

A.19. 17 to 18

  • Removed the unused "external-client-auth-supported" feature.
  • Made client-indentity optional, as there may be over-the-top auth instead.
  • Added augment to uses of local-or-keystore-symmetric-key-grouping for a psk "id" node.
  • Added missing presence container "psks" to ietf-tls-server's "client-authentication" container.
  • Updated examples to reflect new "bag" addition to truststore.
  • Removed feature-limited caseless 'case' statements to improve tree diagram rendering.
  • Refined truststore/keystore groupings to ensure the key formats "must" be particular values.
  • Switched to using truststore's new "public-key" bag (instead of separate "ssh-public-key" and "raw-public-key" bags.
  • Updated client/server examples to cover ALL cases (local/ref x cert/raw-key/psk).

A.20. 18 to 19

  • Updated the "keepalives" containers in part to address Michal Vasko's request to align with RFC 8071, and in part to better align to RFC 6520.
  • Removed algorithm-mapping tables from the "TLS Common Model" section
  • Removed the 'algorithm' node from the examples.
  • Renamed both "client-certs" and "server-certs" to "ee-certs"
  • Added a "Note to Reviewers" note to first page.

A.21. 19 to 20

  • Modified the 'must' expression in the "ietf-tls-client:server-authention" node to cover the "raw-public-keys" and "psks" nodes also.
  • Added a "must 'ca-certs or ee-certs or raw-public-keys or psks'" statement to the ietf-tls-server:client-authentication" node.
  • Added "mandatory true" to "choice auth-type" and a "presence" statement to its ancestor.
  • Expanded "Data Model Overview section(s) [remove "wall" of tree diagrams].
  • Moved the "ietf-ssh-common" module section to proceed the other two module sections.
  • Updated the Security Considerations section.

A.22. 20 to 21

  • Updated examples to reflect new "cleartext-" prefix in the crypto-types draft.

A.23. 21 to 22

  • In both the "client-authentication" and "server-authentication" subtrees, replaced the "psks" node from being a P-container to a leaf of type "empty".
  • Cleaned up examples (e.g., removed FIXMEs)
  • Fixed issues found by the SecDir review of the "keystore" draft.
  • Updated the "psk" sections in the "ietf-tls-client" and "ietf-tls-server" modules to more correctly reflect RFC 4279.

A.24. 22 to 23

  • Addressed comments raised by YANG Doctor in the ct/ts/ks drafts.

A.25. 23 to 24

  • Added missing reference to "FIPS PUB 180-4".
  • Added identity "tls-1.3" and updated description statement in other identities indicating that the protocol version is obsolete and enabling the feature is NOT RECOMMENDED.
  • Added XML-comment above examples explaining the reason for the unexpected top-most element's presence.
  • Added missing "client-ident-raw-public-key" and "client-ident-psk" featutes.
  • Aligned modules with `pyang -f` formatting.
  • Fixed nits found by YANG Doctor reviews.
  • Added a 'Contributors' section.

Acknowledgements

The authors would like to thank for following for lively discussions on list and in the halls (ordered by first name): Alan Luchuk, Andy Bierman, Balazs Kovacs, Benoit Claise, Bert Wijnen, David Lamparter, Dhruv Dhody, Gary Wu, Henk Birkholz, Juergen Schoenwaelder, Ladislav Lhotka, Liang Xia, Martin Bjoerklund, Mehmet Ersue, Michal Vasko, Phil Shafer, Radek Krejci, Sean Turner, and Tom Petch.

Contributors

Special acknowledgement goes to Gary Wu who contributed the "ietf-tls-common" module.

Author's Address

Kent Watsen
Watsen Networks