Internet Engineering Task Force (IETF) K. Watsen

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

YANG Groupings for TLS Clients and TLS Servers

Abstract

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

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

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

Status of This Memo

This is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9645.

Copyright Notice

Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Revised BSD License text as described in Section 4.e of the
Trust Legal Provisions and are provided without warranty as described
in the Revised BSD License.

Table of Contents

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

1. Introduction

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

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

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

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

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

1.1. Regarding the Three IETF Modules

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

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

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

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

1.2. Relation to Other RFCs

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

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

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

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

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

Table 1: Labels in Diagram to RFC Mapping

1.3. Specification Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

1.4. Adherence to the NMDA

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

1.5. Conventions

Various examples in this document use "BASE64VALUE=" as a placeholder
value for binary data that has been base64 encoded (per Section 9.8
of [RFC7950]). This placeholder value is used because real
base64-encoded structures are often many lines long and hence
distracting to the example being presented.

Various examples in this document use the XML [W3C.REC-xml-20081126]
encoding. Other encodings, such as JSON [RFC8259], could
alternatively be used.

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

2. The "ietf-tls-common" Module

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

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

2.1. Data Model Overview

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

2.1.1. Features

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

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

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

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

2.1.2. Identities

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

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

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

Comments:

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

2.1.3. Groupings

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

* hello-params-grouping

This grouping is presented in the following subsection.

2.1.3.1. The "hello-params-grouping" Grouping

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

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

Comments:

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

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

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

2.1.4. Protocol-Accessible Nodes

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

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

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

Comments:

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

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

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

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

2.2. Example Usage

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




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

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

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

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

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

REQUEST

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

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

RESPONSE

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

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

2.3. YANG Module

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

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

<CODE BEGINS> file "[email protected]"
module ietf-tls-common {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-tls-common";
prefix tlscmn;

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

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

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

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

contact
"WG List: NETCONF WG list <mailto:[email protected]>
WG Web: https://datatracker.ietf.org/wg/netconf
Author: Kent Watsen <mailto:[email protected]>
Author: Jeff Hartley <mailto:[email protected]>
Author: Gary Wu <mailto:[email protected]>";

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

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

Copyright (c) 2024 IETF Trust and the persons identified
as authors of the code. All rights reserved.

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

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

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

// Features

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

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

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

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

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

// Identities

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

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

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

// Typedefs

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

// Groupings

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

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

// Protocol-accessible Nodes

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

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

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

}
<CODE ENDS>

3. The "ietf-tls-client" Module

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

3.1. Data Model Overview

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

3.1.1. Features

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

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

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

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

3.1.2. Groupings

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

* tls-client-grouping

This grouping is presented in the following subsection.

3.1.2.1. The "tls-client-grouping" Grouping

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

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

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

Comments:

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

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

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

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

* For the referenced grouping statement(s):

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

3.1.3. Protocol-Accessible Nodes

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

3.2. Example Usage

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

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

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




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


<client-identity>
<certificate>
<inline-definition>
<private-key-format>ct:rsa-private-key-format</priva\
te-key-format>
<cleartext-private-key>BASE64VALUE=</cleartext-priva\
te-key>
<cert-data>BASE64VALUE=</cert-data>
</inline-definition>
</certificate>
</client-identity>


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

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

</tls-client>

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

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




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


<client-identity>
<certificate>
<central-keystore-reference>
<asymmetric-key>rsa-asymmetric-key</asymmetric-key>
<certificate>ex-rsa-cert</certificate>
</central-keystore-reference>
</certificate>
</client-identity>


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

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

</tls-client>

3.3. YANG Module

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

<CODE BEGINS> file "[email protected]"
module ietf-tls-client {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-tls-client";
prefix tlsc;

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

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

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

Copyright (c) 2024 IETF Trust and the persons identified
as authors of the code. All rights reserved.

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

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

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

// Features

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

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

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

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

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

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

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

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

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

// Groupings

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

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

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

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

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

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

}
<CODE ENDS>

4. The "ietf-tls-server" Module

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

4.1. Data Model Overview

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

4.1.1. Features

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

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

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

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

4.1.2. Groupings

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

* tls-server-grouping

This grouping is presented in the following subsection.

4.1.2.1. The "tls-server-grouping" Grouping

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

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

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

Comments:

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

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

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

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

* For the referenced grouping statement(s):

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

4.1.3. Protocol-Accessible Nodes

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

4.2. Example Usage

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

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

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




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


<server-identity>
<certificate>
<inline-definition>
<private-key-format>ct:rsa-private-key-format</private\
-key-format>
<cleartext-private-key>BASE64VALUE=</cleartext-private\
-key>
<cert-data>BASE64VALUE=</cert-data>
</inline-definition>
</certificate>
</server-identity>


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

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

</tls-server>

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

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




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


<server-identity>
<certificate>
<central-keystore-reference>
<asymmetric-key>rsa-asymmetric-key</asymmetric-key>
<certificate>ex-rsa-cert</certificate>
</central-keystore-reference>
</certificate>
</server-identity>


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

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

</tls-server>

4.3. YANG Module

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

<CODE BEGINS> file "[email protected]"
module ietf-tls-server {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-tls-server";
prefix tlss;

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

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

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

Copyright (c) 2024 IETF Trust and the persons identified
as authors of the code. All rights reserved.

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

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

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

// Features

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

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

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

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

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

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

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

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

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

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

// Groupings

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

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

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

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

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

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

}
<CODE ENDS>

5. Security Considerations

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

6. IANA Considerations

6.1. The IETF XML Registry

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

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

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

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

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

6.2. The YANG Module Names Registry

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

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

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

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

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

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

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

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

IANA has added the following note to the registry:

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

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

enum
Replicates a name from the registry.

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

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

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

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

Unassigned or reserved values are not present in the module.

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

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

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

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

7. References

7.1. Normative References

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

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

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

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

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

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

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

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

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

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

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

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

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

[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.

[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.

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

[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.

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

[RFC9640] Watsen, K., "YANG Data Types and Groupings for
Cryptography", RFC 9640, DOI 10.17487/RFC9640, October
2024, <https://www.rfc-editor.org/info/rfc9640>.

[RFC9641] Watsen, K., "A YANG Data Model for a Truststore",
RFC 9641, DOI 10.17487/RFC9641, October 2024,
<https://www.rfc-editor.org/info/rfc9641>.

[RFC9642] Watsen, K., "A YANG Data Model for a Keystore", RFC 9642,
DOI 10.17487/RFC9642, October 2024,
<https://www.rfc-editor.org/info/rfc9642>.

7.2. Informative References

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

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

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

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

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

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

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

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

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

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

[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.

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

[RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of
Documents Containing YANG Data Models", BCP 216, RFC 8407,
DOI 10.17487/RFC8407, October 2018,
<https://www.rfc-editor.org/info/rfc8407>.

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

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

[RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/info/rfc9110>.

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

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

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

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

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

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

Appendix A. Script to Generate IANA-Maintained YANG Modules

This section is not normative.

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

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

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

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

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

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

def create_module_begin(module, f):

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

organization
"Internet Assigned Numbers Authority (IANA)";

contact
"Postal: ICANN
12025 Waterfront Drive, Suite 300
Los Angeles, CA 90094-2536
United States of America
Tel: +1 310 301 5800
Email: <[email protected]>";

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

Copyright (c) 2024 IETF Trust and the persons identified as
authors of the code. All rights reserved.

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

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

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

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

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

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

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

def create_module_body(module, f):

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

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

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

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

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

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

else:

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

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

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

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

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

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

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

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

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

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

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

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

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

def create_module_end(module, f):

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

def create_module(module):

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

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

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

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

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

Acknowledgements

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

Contributors

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

Author's Address

Kent Watsen
Watsen Networks
Email: [email protected]