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NETCONF Working Group                                          K. Watsen
Internet-Draft                                           Watsen Networks
Intended status: Standards Track                                   G. Wu
Expires: 11 January 2021                                   Cisco Systems
                                                            10 July 2020


             YANG Groupings for TLS Clients and TLS Servers
                draft-ietf-netconf-tls-client-server-21

Abstract

   This document defines three YANG modules: the first defines groupings
   for a generic TLS client, the second defines groupings for a generic
   TLS server, and the third defines common identities and groupings
   used by both the client and the server.  It is intended that these
   groupings will be used by applications using the TLS protocol.

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:

   *  "2020-07-10" --> the publication date of this draft

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




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   *  Appendix A.  Change Log

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 11 January 2021.

Copyright Notice

   Copyright (c) 2020 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 Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Relation to other RFCs  . . . . . . . . . . . . . . . . .   4
     1.2.  Specification Language  . . . . . . . . . . . . . . . . .   6
     1.3.  Adherence to the NMDA . . . . . . . . . . . . . . . . . .   6
   2.  The "ietf-tls-common" Module  . . . . . . . . . . . . . . . .   6
     2.1.  Data Model Overview . . . . . . . . . . . . . . . . . . .   7
     2.2.  Example Usage . . . . . . . . . . . . . . . . . . . . . .   9
     2.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  10
   3.  The "ietf-tls-client" Module  . . . . . . . . . . . . . . . .  19
     3.1.  Data Model Overview . . . . . . . . . . . . . . . . . . .  19
     3.2.  Example Usage . . . . . . . . . . . . . . . . . . . . . .  21
     3.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  24
   4.  The "ietf-tls-server" Module  . . . . . . . . . . . . . . . .  32



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     4.1.  Data Model Overview . . . . . . . . . . . . . . . . . . .  32
     4.2.  Example Usage . . . . . . . . . . . . . . . . . . . . . .  35
     4.3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .  39
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  46
     5.1.  The "ietf-tls-common" YANG Module . . . . . . . . . . . .  46
     5.2.  The "ietf-tls-client" YANG Module . . . . . . . . . . . .  47
     5.3.  The "ietf-tls-server" YANG Module . . . . . . . . . . . .  48
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  49
     6.1.  The "IETF XML" Registry . . . . . . . . . . . . . . . . .  49
     6.2.  The "YANG Module Names" Registry  . . . . . . . . . . . .  49
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  49
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  49
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  51
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  53
     A.1.  00 to 01  . . . . . . . . . . . . . . . . . . . . . . . .  53
     A.2.  01 to 02  . . . . . . . . . . . . . . . . . . . . . . . .  53
     A.3.  02 to 03  . . . . . . . . . . . . . . . . . . . . . . . .  53
     A.4.  03 to 04  . . . . . . . . . . . . . . . . . . . . . . . .  53
     A.5.  04 to 05  . . . . . . . . . . . . . . . . . . . . . . . .  54
     A.6.  05 to 06  . . . . . . . . . . . . . . . . . . . . . . . .  54
     A.7.  06 to 07  . . . . . . . . . . . . . . . . . . . . . . . .  54
     A.8.  07 to 08  . . . . . . . . . . . . . . . . . . . . . . . .  54
     A.9.  08 to 09  . . . . . . . . . . . . . . . . . . . . . . . .  54
     A.10. 09 to 10  . . . . . . . . . . . . . . . . . . . . . . . .  55
     A.11. 10 to 11  . . . . . . . . . . . . . . . . . . . . . . . .  55
     A.12. 11 to 12  . . . . . . . . . . . . . . . . . . . . . . . .  55
     A.13. 12 to 13  . . . . . . . . . . . . . . . . . . . . . . . .  55
     A.14. 12 to 13  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.15. 13 to 14  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.16. 14 to 15  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.17. 15 to 16  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.18. 16 to 17  . . . . . . . . . . . . . . . . . . . . . . . .  56
     A.19. 17 to 18  . . . . . . . . . . . . . . . . . . . . . . . .  57
     A.20. 18 to 19  . . . . . . . . . . . . . . . . . . . . . . . .  57
     A.21. 19 to 20  . . . . . . . . . . . . . . . . . . . . . . . .  57
     A.22. 20 to 21  . . . . . . . . . . . . . . . . . . . . . . . .  58
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  58
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  58













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1.  Introduction

   This document defines three YANG 1.1 [RFC7950] modules: the first
   defines a grouping for a generic TLS client, the second defines a
   grouping for a generic TLS server, and the third defines identities
   and groupings common to both the client and the server (TLS is
   defined in [RFC5246]).  It is intended that these groupings will be
   used by applications using the TLS protocol.  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 define
   configuration modules for 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 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.  Links the each RFC are
   provided below the diagram.














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                                  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          | [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] |
   +-----------------------+-------------------------------------------+

                       Table 1: Label to RFC Mapping





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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 in 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):
















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   *  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

2.1.1.  Features

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










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   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
     +-- 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.



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   *  These base identities are "abstract", in the object orientied
      programming sense, in that they only define a "class" of things,
      rather than a specific thing.

2.1.3.  Groupings

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

   Groupings:
     +-- hello-params-grouping

   Each of these groupings are presented in the following subsections.

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 does not contain any protocol-accessible
   nodes, but the module needs to be "implemented", as described in
   Section 5.6.5 of [RFC7950], in order for the identities in
   Section 2.1.2 to be defined.

2.2.  Example Usage

   This section shows how it would appear if the "hello-params-grouping"
   grouping were populated with some data.



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   <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], and [RFC8422].

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

   <CODE BEGINS> file "ietf-tls-common@2020-07-10.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) 2020 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



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        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 2020-07-10 {
       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.";
       reference
         "RFC 2246: The TLS Protocol Version 1.0";
     }

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

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

     feature tls-1_3 {



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       description
         "TLS Protocol Version 1.2 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)";
     }




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     // 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 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";



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     }

     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



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                    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.";



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       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;



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       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



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     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";
         }
       }
     }
   }

   <CODE ENDS>




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3.  The "ietf-tls-client" Module

3.1.  Data Model Overview

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
     +-- x509-certificate-auth
     +-- raw-public-key-auth
     +-- psk-auth

3.1.2.  Groupings

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

   Groupings:
     +-- tls-client-grouping

   Each of these groupings are presented in the following subsections.

3.1.2.1.  The "tls-client-grouping" Grouping

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





















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

     grouping tls-client-grouping
       +-- client-identity!
       |  +-- (auth-type)
       |     +--:(certificate) {x509-certificate-auth}?
       |     |  +-- certificate
       |     |     +---u ks:local-or-keystore-end-entity-cert-with-key-\
   grouping
       |     +--:(raw-public-key) {raw-public-key-auth}?
       |     |  +-- raw-private-key
       |     |     +---u ks:local-or-keystore-asymmetric-key-grouping
       |     +--:(psk) {psk-auth}?
       |        +-- psk
       |           +---u ks:local-or-keystore-symmetric-key-grouping
       +-- server-authentication
       |  +-- ca-certs! {x509-certificate-auth}?
       |  |  +---u ts:local-or-truststore-certs-grouping
       |  +-- ee-certs! {x509-certificate-auth}?
       |  |  +---u ts:local-or-truststore-certs-grouping
       |  +-- raw-public-keys! {raw-public-key-auth}?
       |  |  +---u ts:local-or-truststore-public-keys-grouping
       |  +-- psks! {psk-auth}?
       +-- 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.






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   *  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):

      -  The "local-or-keystore-end-entity-cert-with-key-grouping"
         grouping is discussed in Section 2.1.3.6 of
         [I-D.ietf-netconf-keystore].
      -  The "local-or-keystore-asymmetric-key-grouping" grouping is
         discussed in Section 2.1.3.4 of [I-D.ietf-netconf-keystore].
      -  The "local-or-keystore-symmetric-key-grouping" grouping is
         discussed in Section 2.1.3.3 of [I-D.ietf-netconf-keystore].
      -  The "local-or-truststore-certs-grouping" grouping is discussed
         in Section 2.1.3.1 of [I-D.ietf-netconf-trust-anchors].
      -  The "local-or-truststore-public-keys-grouping" grouping is
         discussed in Section 2.1.3.2 of
         [I-D.ietf-netconf-trust-anchors].
      -  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 does not contain any 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 ================

   <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>



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         <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>



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           <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 ================

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

     <!-- how this client will authenticate itself to the server -->
     <client-identity>



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       <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].




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   <CODE BEGINS> file "ietf-tls-client@2020-07-10.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 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 2020-07-10; // 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



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

        Copyright (c) 2020 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 2020-07-10 {
       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 x509-certificate-auth {
       description
         "Indicates that the client supports authenticating servers



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          using X.509 certificates.";
     }

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

     feature psk-auth {
       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 descendent
          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 TLS-level client authentication
            is sent.  Present so that the 'choice' node's
            mandatory true doesn't imply that a client
            identity 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



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            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.";
             /* FIXME: delete now?
              Not mandatory as client identity MAY be provided
              by another layer in the protocol stack (e.g., an
              HTTP authentication mechanism).";*/
           case certificate {
             if-feature x509-certificate-auth;
             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 raw-public-key-auth;
             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"';



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                 }
               }
             }
           }
           case psk {
             if-feature psk-auth;
             container psk {
               description
                 "Specifies the client identity using a PSK (pre-shared
                 or pairwise-symmetric key).  Note that, when the PSK is
                 configured as a Keystore reference, the key's 'name'
                 node MAY be used as the PSK's ID when used by the TLS
                 protocol.";
               uses ks:local-or-keystore-symmetric-key-grouping {
                 augment "local-or-keystore/local/local-definition" {
                   if-feature "ks:local-definitions-supported";
                   description
                     "Adds an 'id' value when the PSK is used by TLS.";
                   leaf id {
                     type string;  // FIXME: is this the right type?
                     description
                       "The key id used in the TLS protocol for PSKs.";
                   }
                 }
               }
             }
           }
         }
       } // 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 "x509-certificate-auth";
           presence
             "Indicates that the TLS client can authenticate TLS servers
              using configured certificate authority certificates.";
           description
             "A set of certificate authority (CA) certificates used by



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              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 { // FIXME: plural too much?
           if-feature "x509-certificate-auth";
           presence
             "Indicates that the TLS client can authenticate TLS
              servers using configured server certificates.";
           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 "raw-public-key-auth";
           presence
             "Indicates that the TLS client can authenticate TLS
              servers using configured server certificates.";
           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"';
             }
           }
         }
         container psks {



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           if-feature "psk-auth";
           presence
             "Indicates that the TLS client can authenticate TLS servers
              using a configure PSK (pre-shared or pairwise-symmetric
              key).";
           description
             "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";



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           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
   } // module ietf-tls-client

   <CODE ENDS>

4.  The "ietf-tls-server" Module

4.1.  Data Model Overview

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
     +-- client-auth-config-supported
     +-- x509-certificate-auth
     +-- raw-public-key-auth
     +-- psk-auth







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4.1.2.  Groupings

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

   Groupings:
     +-- tls-server-grouping

   Each of these groupings are presented in the following subsections.

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) {x509-certificate-auth}?
       |     |  +-- certificate
       |     |     +---u ks:local-or-keystore-end-entity-cert-with-key-\
   grouping
       |     +--:(raw-private-key) {raw-public-key-auth}?
       |     |  +-- raw-private-key
       |     |     +---u ks:local-or-keystore-asymmetric-key-grouping
       |     +--:(psk) {psk-auth}?
       |        +-- psk
       |           +---u ks:local-or-keystore-symmetric-key-grouping
       +-- client-authentication! {client-auth-config-supported}?
       |  +-- ca-certs! {x509-certificate-auth}?
       |  |  +---u ts:local-or-truststore-certs-grouping
       |  +-- ee-certs! {x509-certificate-auth}?
       |  |  +---u ts:local-or-truststore-certs-grouping
       |  +-- raw-public-keys! {raw-public-key-auth}?
       |  |  +---u ts:local-or-truststore-public-keys-grouping
       |  +-- psks! {psk-auth}?
       +-- 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:




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   *  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):

      -  The "local-or-keystore-end-entity-cert-with-key-grouping"
         grouping is discussed in Section 2.1.3.6 of
         [I-D.ietf-netconf-keystore].
      -  The "local-or-keystore-asymmetric-key-grouping" grouping is
         discussed in Section 2.1.3.4 of [I-D.ietf-netconf-keystore].
      -  The "local-or-keystore-symmetric-key-grouping" grouping is
         discussed in Section 2.1.3.3 of [I-D.ietf-netconf-keystore].
      -  The "local-or-truststore-public-keys-grouping" grouping is
         discussed in Section 2.1.3.2 of
         [I-D.ietf-netconf-trust-anchors].
      -  The "local-or-truststore-certs-grouping" grouping is discussed
         in Section 2.1.3.1 of [I-D.ietf-netconf-trust-anchors].
      -  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 does not contain any protocol-accessible
   nodes.












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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 ================

   <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>



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           <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>



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       <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:







































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

   <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>






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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@2020-07-10.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 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 2020-07-10; // 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/>



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        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) 2020 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 2020-07-10 {
       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.";



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     }

     feature client-auth-config-supported {
       description
         "Indicates that the configuration for how to authenticate
          clients can be configured herein, as opposed to in an
          application specific location.  That is, to support the
          consuming data models that prefer to place client
          authentication with client definitions, rather then
          in a data model principally concerned with configuring
          the transport.";
     }

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

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

     feature psk-auth {
       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 descendent
          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



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          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 x509-certificate-auth;
             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 raw-public-key-auth;
             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"';



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                 }
                 refine "local-or-keystore/keystore/keystore-reference"{
                   must 'deref(.)/../ks:public-key-format'
                        + ' = "ct:subject-public-key-info-format"';
                 }
               }
             }
           }
           case psk {
             if-feature psk-auth;
             container psk {
               description
                 "Specifies the server identity using a PSK (pre-shared
                 or pairwise-symmetric key).  Note that, when the PSK is
                 configured as a Keystore reference, the key's 'name'
                 node MAY be used as the PSK's ID when used by the TLS
                 protocol.";
               uses ks:local-or-keystore-symmetric-key-grouping {
                 augment "local-or-keystore/local/local-definition" {
                   if-feature "ks:local-definitions-supported";
                   description
                     "An 'id' value for when the PSK is used by TLS.";
                   leaf id {
                     type string;  // FIXME: is this the right type?
                     description
                       "The key id used in the TLS protocol for PSKs.";
                   }
                 }
               }
             }
           }
         }
       } // container server-identity

       container client-authentication {
         if-feature "client-auth-config-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



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            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 "x509-certificate-auth";
           presence
             "Indicates that the TLS server can authenticate TLS clients
              using configured certificate authority certificates.";
           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 {   // FIXME: plural too much?
           if-feature "x509-certificate-auth";
           presence
             "Indicates that the TLS server can authenticate TLS
              clients using configured client certificates.";
           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 "raw-public-key-auth";
           presence
             "Indicates that the TLS server can authenticate TLS
              clients using raw public keys.";
           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'



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                    + ' = "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"';
             }
           }
         }
         container psks {
           if-feature "psk-auth";
           presence
             "Indicates that the TLS server can authenticate the TLS
              client using its PSK (pre-shared or pairwise-symmetric
              key).";
           description
             "No configuration is required since the PSK value is the
              same as PSK value configured in the 'client-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



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              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
   } // module ietf-tls-server

   <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.




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   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.

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








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   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.

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

   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.





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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 NETCONF WG of the IETF.
      XML: N/A, the requested URI is an XML namespace.

      URI: urn:ietf:params:xml:ns:yang:ietf-tls-client
      Registrant Contact: The NETCONF WG of the IETF.
      XML: N/A, the requested URI is an XML namespace.

      URI: urn:ietf:params:xml:ns:yang:ietf-tls-server
      Registrant Contact: The NETCONF WG of the IETF.
      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., "Common YANG Data Types for Cryptography",
              Work in Progress, Internet-Draft, draft-ietf-netconf-



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              crypto-types-15, 20 May 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-crypto-
              types-15>.

   [I-D.ietf-netconf-keystore]
              Watsen, K., "A YANG Data Model for a Keystore", Work in
              Progress, Internet-Draft, draft-ietf-netconf-keystore-17,
              20 May 2020, <https://tools.ietf.org/html/draft-ietf-
              netconf-keystore-17>.

   [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-10, 20 May 2020, <https://tools.ietf.org/html/
              draft-ietf-netconf-trust-anchors-10>.

   [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>.

   [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>.

   [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>.






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   [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>.

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-03, 20 May 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-http-
              client-server-03>.

   [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-19, 20 May 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-netconf-
              client-server-19>.

   [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-19, 20 May 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-restconf-
              client-server-19>.

   [I-D.ietf-netconf-ssh-client-server]
              Watsen, K. and G. Wu, "YANG Groupings for SSH Clients and
              SSH Servers", Work in Progress, Internet-Draft, draft-
              ietf-netconf-ssh-client-server-19, 20 May 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-ssh-
              client-server-19>.



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   [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-06, 16 June 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-tcp-
              client-server-06>.

   [I-D.ietf-netconf-tls-client-server]
              Watsen, K. and G. Wu, "YANG Groupings for TLS Clients and
              TLS Servers", Work in Progress, Internet-Draft, draft-
              ietf-netconf-tls-client-server-19, 20 May 2020,
              <https://tools.ietf.org/html/draft-ietf-netconf-tls-
              client-server-19>.

   [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
              RFC 2246, DOI 10.17487/RFC2246, January 1999,
              <https://www.rfc-editor.org/info/rfc2246>.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818,
              DOI 10.17487/RFC2818, May 2000,
              <https://www.rfc-editor.org/info/rfc2818>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <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, April 2006,
              <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, August 2008,
              <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, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [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>.

   [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>.



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   [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>.

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



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   *  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.




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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.//)





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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-config-
      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).







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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.




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Internet-Draft    Groupings for TLS Clients and Servers        July 2020


   *  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.

Acknowledgements

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

Authors' Addresses

   Kent Watsen
   Watsen Networks

   Email: kent+ietf@watsen.net


   Gary Wu
   Cisco Systems

   Email: garywu@cisco.com











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