4. TACACS+ Client Module
この節では TACACS+ client YANG model の RFC テキストを保持し, RFC 9105 changes, TLS 1.3 support, ietf-system-tacacs-plus module, credential references, NACM-sensitive nodes, IANA registrations, JSON examples, full tree を扱う.
RFC 原文
4. TACACS+ Client Module
This YANG module uses types and groupings defined in [RFC8341],
[RFC8343], [RFC8529], [RFC9640], [RFC9641], [RFC9642], [RFC9645], and
[RFC9911].
The module augments [RFC7317].
The module also cites [RFC6520], [RFC9257], and [RFC9258].
<CODE BEGINS> file "[email protected]"
module ietf-system-tacacs-plus {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-system-tacacs-plus";
prefix sys-tcs-plus;
import ietf-inet-types {
prefix inet;
reference
"RFC 9911: Common YANG Data Types";
}
import ietf-yang-types {
prefix yang;
reference
"RFC 9911: Common YANG Data Types";
}
import ietf-system {
prefix sys;
reference
"RFC 7317: A YANG Data Model for System Management";
}
import ietf-netconf-acm {
prefix nacm;
reference
"RFC 8341: Network Configuration Access Control Model";
}
import ietf-interfaces {
prefix if;
reference
"RFC 8343: A YANG Data Model for Interface Management";
}
import ietf-network-instance {
prefix ni;
reference
"RFC 8529: YANG Data Model for Network Instances";
}
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";
}
import ietf-tls-client {
prefix tlsc;
reference
"RFC 9645: YANG Groupings for TLS Clients and TLS Servers";
}
organization
"IETF OPSAWG (Operations and Management Area Working Group)";
contact
"WG Web: <https://datatracker.ietf.org/wg/opsawg/>
WG List: <mailto:[email protected]>
Editor: Mohamed Boucadair
<mailto:[email protected]>
Author: Bo Wu
<[email protected]>
Author: Guangying Zheng
<[email protected]>";
description
"This module provides management of TACACS+ clients.
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) 2026 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).
All revisions of IETF and IANA published modules can be found
at the 'YANG Parameters' registry group:
<https://www.iana.org/assignments/yang-parameters>.
This version of this YANG module is part of RFC 9950; see the
RFC itself for full legal notices.";
revision 2026-03-31 {
description
"This revision adds TLS support. Specifically, this revision
adds:
- a new feature 'credential-reference'
- a new container 'client-credentials'
- a new container 'server-credentials'
- a new leaf 'domain-name'
- a new leaf 'sni-enabled'
- TLS as a new security choice
- a new leaf 'discontinuity-time' under 'statistics'
- a new leaf 'cert-errors' under 'statistics'
- a new leaf 'rpk-errors' under 'statistics'
Also, this revision:
- updates the reference for 'tacacs-plus' identity
to also cite RFC 9887
- fixes a 'must' statement under 'tacacs-plus' by adding
a missing prefix
- requires that the list of servers must be unique per
address/port number.
- updates the description of the 'name' under 'server'
list to better reflect the intended use and clarifies
the difference with the new 'domain-name'
- updates the description of the 'address' to be
consistent with the type
- removes the default statement for the 'port' under
'server' list because a distinct default port number
is used for TACACS+ over TLS
- updates the 'port' leaf under 'server' list to enumerate
the various TACACS+ default port numbers
- adds a constraint on the VRF with 'source-interface'
- updates the description of timeout to remove redundant
text with the default statement";
reference
"RFC 9950: A YANG Data Model for Terminal Access Controller
Access-Control System Plus (TACACS+)";
}
revision 2021-08-05 {
description
"Initial revision.";
reference
"RFC 9105: A YANG Data Model for Terminal Access Controller
Access-Control System Plus (TACACS+)";
}
feature credential-reference {
description
"Indicates whether service credentials references are
supported.";
}
identity tacacs-plus {
base sys:authentication-method;
description
"Indicates AAA operation using TACACS+.";
reference
"RFC 9887: Terminal Access Controller Access-Control
System Plus (TACACS+) over TLS 1.3
RFC 8907: The TACACS+ Protocol";
}
typedef tacacs-plus-server-type {
type bits {
bit authentication {
description
"Indicates that the TACACS+ server is providing
authentication services.";
}
bit authorization {
description
"Indicates that the TACACS+ server is providing
authorization services.";
}
bit accounting {
description
"Indicates that the TACACS+ server is providing accounting
services.";
}
}
description
"The type can be set to authentication, authorization,
accounting, or any combination of the three types.";
}
typedef client-credentials-ref {
type leafref {
path "/sys:system/sys-tcs-plus:tacacs-plus"
+ "/sys-tcs-plus:client-credentials/sys-tcs-plus:id";
}
description
"Defines a type to reference client credentials.";
}
typedef server-credentials-ref {
type leafref {
path "/sys:system/sys-tcs-plus:tacacs-plus"
+ "/sys-tcs-plus:server-credentials/sys-tcs-plus:id";
}
description
"Defines a type to reference server credentials.";
}
grouping statistics {
description
"Grouping for TACACS+ statistics attributes, including TLS
specifics.";
container statistics {
config false;
description
"A collection of server-related statistics objects.";
leaf discontinuity-time {
type yang:date-and-time;
description
"The time of the most recent occasion at which the
TACACS+ client suffered a discontinuity. Examples of
discontinuity can be a configuration action to reset
all counters, re-initialization of the system, or any
other events that prevent reliable contiguous tracking
of counters.";
}
leaf connection-opens {
type yang:counter64;
description
"Number of new connection requests sent to the server,
e.g., socket open.";
}
leaf connection-closes {
type yang:counter64;
description
"Number of connection close requests sent to the server,
e.g., socket close.";
}
leaf connection-aborts {
type yang:counter64;
description
"Number of aborted connections to the server. These do
not include connections that are closed gracefully.";
}
leaf connection-failures {
type yang:counter64;
description
"Number of connection failures to the server.";
}
leaf connection-timeouts {
type yang:counter64;
description
"Number of connection timeouts to the server.";
}
leaf messages-sent {
type yang:counter64;
description
"Number of messages sent to the server.";
}
leaf messages-received {
type yang:counter64;
description
"Number of messages received from the server.";
}
leaf errors-received {
type yang:counter64;
description
"Number of error messages received from the server.";
}
leaf sessions {
type yang:counter64;
description
"Number of TACACS+ sessions completed with the server.
If the Single Connection Mode was not enabled, the number
of sessions is the same as the number of
'connection-closes'. If the Single Connection Mode was
enabled, a single TCP connection may contain multiple
TACACS+ sessions.";
}
leaf cert-errors {
type yang:counter64;
description
"Number of connection failures due to certificate
issues.";
}
leaf rpk-errors {
if-feature "tlsc:server-auth-raw-public-key";
type yang:counter64;
description
"Number of connection failures related to raw public
keys.";
}
}
}
grouping certificate {
description
"Specifies a certificate that can be used for client
identity.";
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")';
}
}
}
grouping raw-private-key {
description
"Specifies a raw private key that can be used for
client identity.";
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")';
}
}
}
grouping 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).
When Pre-Shared Keys (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.";
reference
"RFC 8446: The Transport Layer Security (TLS) Protocol
Version 1.3, Section 4.2.11
RFC 9257: Guidance for External Pre-Shared Key (PSK) Usage
in TLS, Section 6
RFC 9258: Importing External Pre-Shared Keys (PSKs) for
TLS 1.3, Section 5.1";
uses ks:inline-or-keystore-symmetric-key-grouping;
leaf external-identity {
type string;
mandatory true;
description
"A sequence of bytes used to identify an EPSK. A label for
a PSK established externally.";
reference
"RFC 8446: The Transport Layer Security (TLS) Protocol
Version 1.3, Section 4.2.11
RFC 9257: Guidance for External Pre-Shared Key (PSK)
Usage in TLS, Section 4.1";
}
leaf hash {
type tlscmn:epsk-supported-hash;
default "sha-256";
description
"For externally established PSKs, the hash algorithm must be
set when the PSK is established or default to SHA-256 if no
such algorithm is defined.";
reference
"RFC 8446: The Transport Layer Security (TLS) Protocol
Version 1.3, Section 4.2.11";
}
leaf context {
type string;
description
"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.";
reference
"RFC 9258: Importing External Pre-Shared Keys (PSKs) for
TLS 1.3, Section 5.1 ";
}
leaf target-protocol {
type uint16;
description
"Specifies the protocol for which a PSK is imported for
use.";
reference
"RFC 9258: Importing External Pre-Shared Keys (PSKs) for
TLS 1.3, Section 3 ";
}
leaf target-kdf {
type uint16;
description
"The KDF for which a PSK is imported for use.";
reference
"RFC 9258: Importing External Pre-Shared Keys (PSKs) for
TLS 1.3, Section 3";
}
}
grouping client-identity {
description
"Identity credentials that a TLS client may present when
establishing a connection to a TLS server. When configured
and requested by the TLS server when establishing a TLS
session, these credentials are passed in the Certificate
message.";
reference
"RFC 8446: The Transport Layer Security (TLS) Protocol
Version 1.3, Section 4.4.2";
choice auth-type {
description
"A choice amongst authentication types.";
case certificate {
container certificate {
description
"Specifies the client identity using a certificate.";
uses certificate;
}
}
case raw-public-key {
if-feature "tlsc:client-ident-raw-public-key";
container raw-private-key {
description
"Specifies the client identity using a raw public key.";
uses raw-private-key;
}
}
case tls13-epsk {
if-feature "tlsc:client-ident-tls13-epsk";
container tls13-epsk {
description
"An EPSK is established or provisioned out of band.";
uses tls13-epsk;
}
}
}
}
grouping client-identity-with-ref {
description
"Identity credentials that the TLS client may present when
establishing a connection to a TLS server. When configured
and requested by the TLS server when establishing a TLS
session, these credentials are passed in the Certificate
message.";
choice ref-or-explicit {
description
"A choice between a reference or explicit configuration.";
case ref {
description
"Provides a reference to a client identity.";
leaf credentials-reference {
if-feature "credential-reference";
type sys-tcs-plus:client-credentials-ref;
description
"Specifies the client credentials reference.";
}
}
case explicit {
description
"Explicit configuration of the client identity.";
uses client-identity;
}
}
}
grouping server-authentication {
description
"Specifies how a TLS client can authenticate TLS servers.
Any combination of credentials is additive and unordered.";
container ca-certs {
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 {
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., end entity certificates)
used by a 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 "tlsc: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 a 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 tls13-epsks {
if-feature "tlsc:server-auth-tls13-epsk";
type empty;
description
"Indicates that a TLS client can authenticate TLS servers
using configured EPSKs.";
}
}
grouping server-authentication-with-ref {
description
"Specifies how a TLS client can authenticate TLS servers.";
choice ref-or-explicit {
description
"A choice between a reference or explicit configuration.";
case ref {
description
"Provides a reference to server credentials.";
leaf credentials-reference {
if-feature "credential-reference";
type sys-tcs-plus:server-credentials-ref;
description
"Specifies the server credentials reference.";
}
}
case explicit {
description
"Explicit configuration of credentials of a server.";
uses server-authentication;
}
}
}
grouping hello-params {
description
"Configurable parameters for the TLS Hello message.";
reference
"RFC 9887: Terminal Access Controller Access-Control
System Plus (TACACS+) over TLS 1.3,
Section 5.1";
uses tlscmn:hello-params-grouping {
refine "tls-versions/min" {
must "not(derived-from-or-self(current(), "
+ "'tlscmn:tls12'))" {
error-message
"TLS 1.2 is not supported as min TLS version";
}
}
refine "tls-versions/max" {
must "not(derived-from-or-self(current(), "
+ "'tlscmn:tls12'))" {
error-message
"TLS 1.2 is not supported as max TLS version";
}
}
}
}
grouping tls-client {
description
"A grouping for configuring a TLS client without any
consideration for how an underlying TCP session is
established.";
container client-identity {
presence "Indicates that a TLS-level client identity has been
configured.
This statement is present so the mandatory descendant
do not imply that this node must be configured.";
description
"Identity credentials that a TLS client may present when
establishing a connection to a TLS server.";
uses client-identity-with-ref;
}
container server-authentication {
must 'credentials-reference or ca-certs or ee-certs or '
+ 'raw-public-keys or tls13-epsks';
description
"Specifies how a TLS client can authenticate TLS servers.";
uses server-authentication-with-ref;
}
container hello-params {
if-feature "tlscmn:hello-params";
description
"Configurable parameters for the TLS Hello message.";
uses hello-params;
}
}
grouping tacacs-plus {
description
"Grouping for TACACS+ attributes.";
container tacacs-plus {
must "not(derived-from-or-self(../sys:authentication"
+ "/sys:user-authentication-order, "
+ "'sys-tcs-plus:tacacs-plus'))"
+ " or bit-is-set(server/server-type,'authentication')" {
error-message
"When 'tacacs-plus' is used as a system authentication
method, a TACACS+ authentication server must be
configured.";
description
"When 'tacacs-plus' is used as an authentication method,
a TACACS+ server must be configured.";
}
description
"Container for TACACS+ configurations and operations.";
list client-credentials {
if-feature "credential-reference";
key "id";
description
"Identity credentials that a TLS client may present
when establishing a connection to a TLS server.
A list of client credentials that can be referenced
when configuring server instances.";
nacm:default-deny-write;
leaf id {
type string;
description
"An identifier that uniquely identifies a client
identity within the device configuration.";
}
uses client-identity;
}
list server-credentials {
if-feature "credential-reference";
key "id";
description
"Identity credentials that a TLS client may use
to authenticate a TLS server.";
nacm:default-deny-write;
leaf id {
type string;
description
"An identifier that uniquely identifies server
credentials within the device configuration.";
}
uses server-authentication;
}
list server {
key "name";
unique "address port";
ordered-by user;
description
"List of TACACS+ servers used by the device.";
leaf name {
type string;
description
"A name that is used to uniquely identify a TACACS+
server within the device configuration.
This name is not to be confused with the
'domain-name'.";
}
leaf server-type {
type tacacs-plus-server-type;
mandatory true;
description
"The server type can be authentication, authorization,
accounting, or any combination of the three types.";
}
leaf domain-name {
type inet:domain-name;
description
"Provides a domain name of the TACACS+ server.";
reference
"RFC 9887: Terminal Access Controller Access-Control
System Plus (TACACS+) over TLS 1.3,
Section 3.4.2";
}
leaf sni-enabled {
type boolean;
must '../domain-name' {
error-message
"A domain name must be provided to make use of Server
Name Indication (SNI).";
}
description
"Enables the use of SNI when set to true. Disables the
use of SNI when set to false.";
reference
"RFC 6066: Transport Layer Security (TLS) Extensions:
Extension Definitions, Section 3
RFC 9887: Terminal Access Controller Access-Control
System Plus (TACACS+) over TLS 1.3,
Section 3.4.2";
}
leaf address {
type inet:host;
mandatory true;
description
"The IP address or name of the TACACS+ server.";
}
leaf port {
type inet:port-number;
mandatory true;
description
"The port number of the TACACS+ server.
The default port number for legacy TACACS+ is 49,
while it is 300 for TACACS+ over TLS.";
}
choice security {
mandatory true;
description
"Security mechanism between TACACS+ client and server.";
case tls {
description
"TLS is used to secure TACACS+ exchanges.";
reference
"RFC 9887: Terminal Access Controller Access-Control
System Plus (TACACS+) over TLS 1.3";
uses tls-client;
}
case obfuscation {
leaf shared-secret {
type string {
length "1..max";
}
description
"The shared secret, which is known to both the
TACACS+ client and server. TACACS+ server
administrators SHOULD configure a shared secret with
a minimum length of 16 characters.
It is highly recommended that this shared secret is
at least 32 characters long and sufficiently complex
with a mix of different character types,
i.e., upper case, lower case, numeric, and
punctuation. Note that this security mechanism is
best described as 'obfuscation' and not 'encryption'
as it does not provide any meaningful integrity,
privacy, or replay protection.
The use of obfuscation is deprecated in favor
of TLS.
This choice is provided in the model to accommodate
installed base.";
reference
"RFC 8907: The TACACS+ Protocol
RFC 9887: Terminal Access Controller Access-Control
System Plus (TACACS+) over TLS 1.3";
nacm:default-deny-all;
}
}
}
choice source-type {
description
"The source address type for outbound TACACS+ packets.";
case source-ip {
leaf source-ip {
type inet:ip-address;
description
"Specifies the source IP address for TACACS+ outbound
packets.";
}
}
case source-interface {
leaf source-interface {
type if:interface-ref;
description
"Specifies the interface from which the IP address
is derived for use as the source for outbound
TACACS+ packets.";
}
}
}
leaf vrf-instance {
type leafref {
path "/ni:network-instances/ni:network-instance/ni:name";
}
must '(not(../source-interface)) or '
+ '(current() = /if:interfaces/if:interface'
+ '[if:name = current()/../source-interface]'
+ '/ni:bind-ni-name)' {
error-message
"VRF instance must match the network instance of the
source interface.";
}
description
"Specifies the VPN Routing and Forwarding (VRF) instance
to use to communicate with the TACACS+ server.
If 'source-interface' is configured, this value MUST
match the network instance bound to the source interface
(via bind-ni-name).";
reference
"RFC 8529: YANG Data Model for Network Instances";
}
leaf single-connection {
type boolean;
default "false";
description
"Indicates whether the Single Connection Mode is enabled
for the server.";
reference
"RFC 8907: The TACACS+ Protocol, Section 4.3";
}
leaf timeout {
type uint16 {
range "1..max";
}
units "seconds";
default "5";
description
"The number of seconds that the device will wait for a
response from each TACACS+ server before trying with a
different server.";
}
uses statistics;
}
}
}
augment "/sys:system" {
description
"Augments the system model with the tacacs-plus data nodes.";
uses tacacs-plus;
}
}
<CODE ENDS>