Operations and Management Area Working Group M. Boucadair, Ed. Internet-Draft Orange Intended status: Informational 28 May 2024 Expires: 29 November 2024 A YANG Model for Terminal Access Controller Access-Control System Plus (TACACS+) over TLS 1.3 draft-boucadair-opsawg-secure-tacacs-yang-01 Abstract This document defines a YANG module for Terminal Access Controller Access-Control System Plus (TACACS+) over TLS 1.3. This modules augments the YANG Data Model for Terminal Access Controller Access- Control System Plus (TACACS+) defined in the RFC 9105 with TLS- related data nodes. About This Document This note is to be removed before publishing as an RFC. The latest revision of this draft can be found at https://boucadair.github.io/secure-tacacs-yang/draft-boucadair- opsawg-secure-tacacs-yang.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-boucadair- opsawg-secure-tacacs-yang/. Discussion of this document takes place on the Operations and Management Area Working Group Working Group mailing list (mailto:opsawg@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/opsawg/. Subscribe at https://www.ietf.org/mailman/listinfo/opsawg/. Source for this draft and an issue tracker can be found at https://github.com/boucadair/secure-tacacs-yang. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Boucadair Expires 29 November 2024 [Page 1] Internet-Draft YANG for TACACS+ over TLS May 2024 Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 29 November 2024. 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3 3. Module Tree Structure . . . . . . . . . . . . . . . . . . . . 4 4. YANG Module . . . . . . . . . . . . . . . . . . . . . . . . . 9 5. Security Considerations . . . . . . . . . . . . . . . . . . . 19 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 7.1. Normative References . . . . . . . . . . . . . . . . . . 21 7.2. Informative References . . . . . . . . . . . . . . . . . 23 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 23 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 23 1. Introduction [RFC9105] defines a YANG module ("ietf-system-tacacs-plus") that augments the System Management data model defined in [RFC7317] for the management of Terminal Access Controller Access-Control System Plus (TACACS+) clients. Typically, the "ietf-system-tacacs-plus" module is used to configure a TACACS+ client on a device to support deployment scenarios with centralized authentication, authorization, and accounting servers. Boucadair Expires 29 November 2024 [Page 2] Internet-Draft YANG for TACACS+ over TLS May 2024 This document defines a YANG module for managing TACACS+ over TLS 1.3 clients [I-D.ietf-opsawg-tacacs-tls13]. The module is designed as an augmentation to the "ietf-system-tacacs-plus" module specified in [RFC9105]. Discussion Note: RFC 9105bis or keep the current augment design. The module leverages the TLS structures defined in [I-D.ietf-netconf-tls-client-server]. Concretely, this first version of the specification uses a pruning approach rather that a reuse of the groupings defined in [I-D.ietf-netconf-tls-client-server]. 2. Conventions and Definitions 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. The meanings of the symbols in the YANG tree diagrams are defined in [RFC8340]. The document uses the terms defined in Section 2 of [I-D.ietf-opsawg-tacacs-tls13] and Section 3 of [RFC8907]. 'client' refers to TLS TACACS+ client, while 'server' refers to TLS TACACS+ server. Note to the RFC Editor: Please update the following: - AAAA --> the assigned RFC number for [I-D.ietf-netconf-crypto-types] - BBBB --> the assigned RFC number for [I-D.ietf-netconf-trust-anchors] - CCCC --> the assigned RFC number for [I-D.ietf-netconf-keystore] - FFFF --> the assigned RFC number for [I-D.ietf-netconf-tls-client-server] - XXXX --> the assigned RFC number for this document. Boucadair Expires 29 November 2024 [Page 3] Internet-Draft YANG for TACACS+ over TLS May 2024 3. Module Tree Structure The module is designed to cover the following key requirements specified in [I-D.ietf-opsawg-tacacs-tls13]: * TLS 1.3 [RFC8446] MUST be used for transport. * Earlier TLS versions TLS MUST NOT be used. * The cipher suites offered or accepted SHOULD be configurable. * Implementations MAY support Raw Public Keys and PSK. * Implementations MUST support the ability to configure the server's domain name The full tree structure is shown below: =============== NOTE: '\' line wrapping per RFC 8792 ================ module: ietf-system-secure-tacacs augment /sys:system/sys-tcs-plus:tacacs-plus/sys-tcs-plus:server: +--rw remote-address* [address] | +--rw address inet:ip-address | +--rw port-number? inet:port-number +--rw domain-name? inet:domain-name augment /sys:system/sys-tcs-plus:tacacs-plus/sys-tcs-plus:server /sys-tcs-plus:security: +--:(tls) +--rw client-identity! | +--rw (auth-type)? | +--:(certificate) | | +--rw certificate | | +--rw (inline-or-keystore) | | +--:(inline) {inline-definitions-supported}? | | | +--rw inline-definition | | | +--rw public-key-format? | | | | identityref | | | +--rw public-key? | | | | binary | | | +--rw private-key-format? | | | | identityref | | | +--rw (private-key-type) | | | | +--:(cleartext-private-key) | | | | | {cleartext-private-keys}? | | | | | +--rw cleartext-private-key? | | | | | binary Boucadair Expires 29 November 2024 [Page 4] Internet-Draft YANG for TACACS+ over TLS May 2024 | | | | +--:(hidden-private-key) | | | | | {hidden-private-keys}? | | | | | +--rw hidden-private-key? | | | | | empty | | | | +--:(encrypted-private-key) | | | | {encrypted-private-keys}? | | | | +--rw encrypted-private-key | | | | +--rw encrypted-by | | | | +--rw encrypted-value-format | | | | | identityref | | | | +--rw encrypted-value | | | | binary | | | +--rw cert-data? | | | | end-entity-cert-cms | | | +---n certificate-expiration | | | | {certificate-expiration-\ notification}? | | | | +-- expiration-date | | | | yang:date-and-time | | | +---x generate-csr {csr-generation}? | | | +---w input | | | | +---w csr-format identityref | | | | +---w csr-info csr-info | | | +--ro output | | | +--ro (csr-type) | | | +--:(p10-csr) | | | +--ro p10-csr? p10-csr | | +--:(central-keystore) | | {central-keystore-supported,\ asymmetric-keys}? | | +--rw central-keystore-reference | | +--rw asymmetric-key? | | | ks:central-asymmetric-key-ref | | | {central-keystore-supported,\ asymmetric-keys}? | | +--rw certificate? leafref | +--:(raw-public-key) {tlsc:client-ident-raw-public-key}? | | +--rw raw-private-key | | +--rw (inline-or-keystore) | | +--:(inline) {inline-definitions-supported}? | | | +--rw inline-definition | | | +--rw public-key-format? | | | | identityref | | | +--rw public-key? | | | | binary | | | +--rw private-key-format? | | | | identityref | | | +--rw (private-key-type) Boucadair Expires 29 November 2024 [Page 5] Internet-Draft YANG for TACACS+ over TLS May 2024 | | | +--:(cleartext-private-key) | | | | {cleartext-private-keys}? | | | | +--rw cleartext-private-key? | | | | binary | | | +--:(hidden-private-key) | | | | {hidden-private-keys}? | | | | +--rw hidden-private-key? | | | | empty | | | +--:(encrypted-private-key) | | | {encrypted-private-keys}? | | | +--rw encrypted-private-key | | | +--rw encrypted-by | | | +--rw encrypted-value-format | | | | identityref | | | +--rw encrypted-value | | | binary | | +--:(central-keystore) | | {central-keystore-supported,\ asymmetric-keys}? | | +--rw central-keystore-reference? | | ks:central-asymmetric-key-ref | +--:(tls13-epsk) {tlsc:client-ident-tls13-epsk}? | +--rw tls13-epsk | +--rw (inline-or-keystore) | | +--:(inline) {inline-definitions-supported}? | | | +--rw inline-definition | | | +--rw key-format? | | | | identityref | | | +--rw (key-type) | | | +--:(cleartext-symmetric-key) | | | | +--rw cleartext-symmetric-key? | | | | binary | | | | {cleartext-symmetric-keys}? | | | +--:(hidden-symmetric-key) | | | | {hidden-symmetric-keys}? | | | | +--rw hidden-symmetric-key? | | | | empty | | | +--:(encrypted-symmetric-key) | | | {encrypted-symmetric-keys}? | | | +--rw encrypted-symmetric-key | | | +--rw encrypted-by | | | +--rw encrypted-value-format | | | | identityref | | | +--rw encrypted-value | | | binary | | +--:(central-keystore) | | {central-keystore-supported,symmetric\ -keys}? Boucadair Expires 29 November 2024 [Page 6] Internet-Draft YANG for TACACS+ over TLS May 2024 | | +--rw central-keystore-reference? | | ks:central-symmetric-key-ref | +--rw external-identity string | +--rw hash? | | tlscmn:epsk-supported-hash | +--rw context? string | +--rw target-protocol? uint16 | +--rw target-kdf? uint16 +--rw server-authentication | +--rw ca-certs! | | +--rw (inline-or-truststore) | | +--:(inline) {inline-definitions-supported}? | | | +--rw inline-definition | | | +--rw certificate* [name] | | | +--rw name string | | | +--rw cert-data | | | | trust-anchor-cert-cms | | | +---n certificate-expiration | | | {certificate-expiration-\ notification}? | | | +-- expiration-date yang:date-and-time | | +--:(central-truststore) | | {central-truststore-supported,certificates}? | | +--rw central-truststore-reference? | | ts:central-certificate-bag-ref | +--rw ee-certs! | | +--rw (inline-or-truststore) | | +--:(inline) {inline-definitions-supported}? | | | +--rw inline-definition | | | +--rw certificate* [name] | | | +--rw name string | | | +--rw cert-data | | | | trust-anchor-cert-cms | | | +---n certificate-expiration | | | {certificate-expiration-\ notification}? | | | +-- expiration-date yang:date-and-time | | +--:(central-truststore) | | {central-truststore-supported,certificates}? | | +--rw central-truststore-reference? | | ts:central-certificate-bag-ref | +--rw raw-public-keys! {tlsc:server-auth-raw-public-key}? | | +--rw (inline-or-truststore) | | +--:(inline) {inline-definitions-supported}? | | | +--rw inline-definition | | | +--rw public-key* [name] | | | +--rw name string | | | +--rw public-key-format identityref Boucadair Expires 29 November 2024 [Page 7] Internet-Draft YANG for TACACS+ over TLS May 2024 | | | +--rw public-key binary | | +--:(central-truststore) | | {central-truststore-supported,public-keys}? | | +--rw central-truststore-reference? | | ts:central-public-key-bag-ref | +--rw tls13-epsks? empty | {tlsc:server-auth-tls13-epsk}? +--rw hello-params {tlscmn:hello-params}? | +--rw tls-versions | | +--rw min? identityref | | +--rw max? identityref | +--rw cipher-suites | +--rw cipher-suite* tlscsa:tls-cipher-suite-algorithm +--rw keepalives {tlsc:tls-client-keepalives}? +--rw peer-allowed-to-send? empty +--rw test-peer-aliveness! +--rw max-wait? uint16 +--rw max-attempts? uint8 The following data nodes are supported: 'remote-address': Specifies a list of IP address/port numbers that can be used to reach a server instance. A server instance may be identified by an IPv4 address, IPv6 address, or both. One or multiple addresses of the same address family may be provided. The same or distinct port numbers may be used per address family. This container takes precedence over "address" and "port" data nodes defined in [RFC9105]. 'domain-name': Provides a domain name of the server per Section 3.3 of [I-D.ietf-opsawg-tacacs-tls13]. 'client-identity': Specifies the identity credentials that the client may present when establishing a connection to a server. 'server-authentication': Specifies how a client authenticate servers. 'hello-params': Controls TLS versions and cipher suites. 'keepalives': Providers a set of parameters for testing the aliveness of the server. Boucadair Expires 29 November 2024 [Page 8] Internet-Draft YANG for TACACS+ over TLS May 2024 4. YANG Module This module uses types and groupings defined in [RFC6991], [RFC8341], [I-D.ietf-netconf-crypto-types], [I-D.ietf-netconf-trust-anchors], [I-D.ietf-netconf-keystore], and [I-D.ietf-netconf-tls-client-server]. The module augments [RFC9105], which is also an augment of [RFC7317]. The module also cites [RFC9257], [RFC9258], [RFC9258], and [RFC6520]. file "ietf-system-secure-tacacs@2024-05-23.yang" =============== NOTE: '\' line wrapping per RFC 8792 ================ module ietf-system-secure-tacacs { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-system-secure-tacacs"; prefix secure-tacacs; import ietf-inet-types { prefix inet; reference "RFC 6991: Common YANG Data Types"; } import ietf-keystore { prefix ks; reference "RFC CCCC: A YANG Data Model for a Keystore"; } import ietf-truststore { prefix ts; reference "RFC BBBB: A YANG Data Model for a Truststore"; } import ietf-tls-client { prefix tlsc; reference "RFC FFFF: YANG Groupings for TLS Clients and TLS Servers"; } import ietf-netconf-acm { prefix nacm; reference "RFC 8341: Network Configuration Access Control Model"; } import ietf-crypto-types { prefix ct; reference "RFC AAAA: YANG Data Types and Groupings for Cryptography"; Boucadair Expires 29 November 2024 [Page 9] Internet-Draft YANG for TACACS+ over TLS May 2024 } import ietf-tls-common { prefix tlscmn; reference "RFC FFFF: YANG Groupings for TLS Clients and TLS Servers"; } import ietf-system { prefix sys; reference "RFC 7317: A YANG Data Model for System Management"; } import ietf-system-tacacs-plus { prefix sys-tcs-plus; reference "RFC 9105: A YANG Data Model for Terminal Access Controller Access-Control System Plus (TACACS+)"; } organization "IETF OPSAWG (Operations and Management Area Working Group)"; contact "WG Web: WG List: Editor: Mohamed Boucadair "; description "This module provides configuration of TACACS+ over TLS clients. 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 XXXX; see the RFC itself for full legal notices."; revision 2024-05-23 { description "Initial revision."; reference "RFC XXXX: XXXX"; Boucadair Expires 29 November 2024 [Page 10] Internet-Draft YANG for TACACS+ over TLS May 2024 } // to be further tweaked to align with the scope of tacacs+TLS spec // can't reuse the groupings in TLS as they are because TLS1.2 // is not supported // can't set a default because of must in a choice grouping 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")'; } } } grouping 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")'; } } } grouping tls13-epsk { description Boucadair Expires 29 November 2024 [Page 11] Internet-Draft YANG for TACACS+ over TLS May 2024 "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 PSKs are provisioned out of band, the PSK identity and the 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 pre-shared key 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 { Boucadair Expires 29 November 2024 [Page 12] Internet-Draft YANG for TACACS+ over TLS May 2024 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 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."; reference "RFC 8446: The Transport Layer Security (TLS) Protocol Version 1.3, Section 4.4.2"; nacm:default-deny-write; choice auth-type { //default "certificate"; //mandatory true; description "A choice amongst authentication types, of which one must be enabled and selected."; 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 RPK."; uses raw-private-key; Boucadair Expires 29 November 2024 [Page 13] Internet-Draft YANG for TACACS+ over TLS May 2024 } } 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 server-authentication { description "Specifies how the TLS client can authenticate TLS servers. Any combination of credentials is additive and unordered."; nacm:default-deny-write; container ca-certs { presence "Indicates that CA certificates have been configured. This statement is present so the mandatory descendant nodes do not imply that this node must be configured."; description "A set of CA certificates used by the TLS client to authenticate TLS server certificates. A server certificate is authenticated if it has a valid chain of trust to a configured CA certificate."; reference "RFC BBBB: A YANG Data Model for a Truststore"; uses ts:inline-or-truststore-certs-grouping; } container ee-certs { presence "Indicates that EE certificates have been configured. This statement is present so the mandatory descendant nodes do not imply that this node must be configured."; description "A set of server certificates (i.e., end entity certificates) used by the TLS client to authenticate certificates presented by TLS servers. A server certificate is authenticated if it is an exact match to a configured server certificate."; reference "RFC BBBB: A YANG Data Model for a Truststore"; uses ts:inline-or-truststore-certs-grouping; } container raw-public-keys { Boucadair Expires 29 November 2024 [Page 14] Internet-Draft YANG for TACACS+ over TLS May 2024 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 the TLS client to authenticate raw public keys presented by the TLS server. A raw public key is authenticated if it is an exact match to a configured raw public key."; reference "RFC BBBB: A YANG Data Model for a Truststore"; uses ts: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 the TLS client can authenticate TLS servers using configured external PSKs."; } } grouping test-peer-aliveness { description "Configures the keep-alive policy to proactively test the aliveness of the TLS server. An unresponsive TLS server is dropped after approximately max-wait * max-attempts seconds."; reference "RFC 6520: Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension"; leaf max-wait { type uint16 { range "1..max"; Boucadair Expires 29 November 2024 [Page 15] Internet-Draft YANG for TACACS+ over TLS May 2024 } units "seconds"; default "30"; description "Sets the amount of time in seconds after which if no data has been received from the TLS server, a TLS-level message will be sent to test the aliveness of the TLS server."; } leaf max-attempts { type uint8; default "3"; description "Sets the maximum number of sequential keep-alive messages that can fail to obtain a response from the TLS server before assuming the TLS server is no longer alive."; } } grouping hello-params { description "Configurable parameters for the TLS hello message."; nacm:default-deny-write; 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 keepalives { description "Configures the keepalive policy for the TLS client."; nacm:default-deny-write; leaf peer-allowed-to-send { type empty; description "Indicates that the remote TLS server is allowed to send Boucadair Expires 29 November 2024 [Page 16] Internet-Draft YANG for TACACS+ over TLS May 2024 HeartbeatRequest messages to this TLS client."; reference "RFC 6520: Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension"; } container test-peer-aliveness { presence "Indicates that the TLS client proactively tests the aliveness of the remote TLS server."; description "Configures the keep-alive policy to proactively test the aliveness of the TLS server. An unresponsive TLS server is dropped after approximately max-wait * max-attempts seconds."; uses test-peer-aliveness; } } 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 the TLS client may present when establishing a connection to a TLS server."; uses client-identity; } container server-authentication { must 'ca-certs or ee-certs or raw-public-keys or tls13-epsks'; description "Specifies how the TLS client can authenticate TLS servers."; uses server-authentication; } container hello-params { if-feature "tlscmn:hello-params"; description "Configurable parameters for the TLS hello message."; uses hello-params; } container keepalives { if-feature "tlsc:tls-client-keepalives"; Boucadair Expires 29 November 2024 [Page 17] Internet-Draft YANG for TACACS+ over TLS May 2024 description "Configures the keepalive policy for the TLS client."; uses keepalives; } } grouping tcp-server-info { description "A grouping for configuring the information to contact a TCP server."; list remote-address { key "address"; description "A server instance may be reachable using multiple IP address and port numbers. For example, use the same port number in different address families or different port numbers in the same address family."; leaf address { type inet:ip-address; description "The remote IP address to reach a server."; } leaf port-number { type inet:port-number; description "The remote port number of the server."; } } } augment "/sys:system/sys-tcs-plus:tacacs-plus" + "/sys-tcs-plus:server" { description "Adds server's domain name."; uses tcp-server-info { refine "remote-address/address" { must 'not(../../sys-tcs-plus:address)' { error-message "Either use the list of bind points or RFC 9105 address data node, not both."; } } refine "remote-address/port-number" { must 'not(../../sys-tcs-plus:port)' { error-message "Either use the list of bind points or RFC 9105 port data node, not both."; } Boucadair Expires 29 November 2024 [Page 18] Internet-Draft YANG for TACACS+ over TLS May 2024 default "1234"; // to be replaced by TACACS-TLS-PORT } } leaf domain-name { type inet:domain-name; description "Provides a domain name of the TACACS+ server."; } } augment "/sys:system/sys-tcs-plus:tacacs-plus/sys-tcs-plus:server" + "/sys-tcs-plus:security" { description "Adds TLS case."; case tls { description "TLS is used."; uses tls-client; } } } 5. Security Considerations This section uses the template described in Section 3.7 of [I-D.ietf-netmod-rfc8407bis]. The YANG module specified in this document defines schema for data that is designed to be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446]. The Network Configuration Access Control Model (NACM) [RFC8341] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. Boucadair Expires 29 November 2024 [Page 19] Internet-Draft YANG for TACACS+ over TLS May 2024 There are a number of data nodes defined in this YANG module that are writable/creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) and delete operations to these data nodes without proper protection or authentication can have a negative effect on network operations. Specifically, the following subtrees and data nodes have particular sensitivities/vulnerabilities: 'xxx': : xxxx. Some of the readable data nodes in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. Specifically, the following subtrees and data nodes have particular sensitivities/ vulnerabilities: 'xxx': : xxxx. This YANG module uses groupings from other YANG modules that define nodes that may be considered sensitive or vulnerable in network environments. Refer to Section 5.3 of [I-D.ietf-netconf-tls-client-server] for information as to which nodes may be considered sensitive or vulnerable in network environments. 6. IANA Considerations IANA is requested to register the following URI in the "ns" subregistry within the "IETF XML Registry" [RFC3688]: URI: urn:ietf:params:xml:ns:yang:ietf-system-secure-tacacs Registrant Contact: The IESG. XML: N/A; the requested URI is an XML namespace. IANA is requested to register the following YANG module in the "YANG Module Names" registry [RFC6020] within the "YANG Parameters" registry group: Name: ietf-system-secure-tacacs Namespace: urn:ietf:params:xml:ns:yang:ietf-system-secure-tacacs Prefix: secure-tacacs Maintained by IANA? N Reference: RFC XXXX Boucadair Expires 29 November 2024 [Page 20] Internet-Draft YANG for TACACS+ over TLS May 2024 7. References 7.1. Normative References [I-D.ietf-netconf-crypto-types] Watsen, K., "YANG Data Types and Groupings for Cryptography", Work in Progress, Internet-Draft, draft- ietf-netconf-crypto-types-34, 16 March 2024, . [I-D.ietf-netconf-keystore] Watsen, K., "A YANG Data Model for a Keystore and Keystore Operations", Work in Progress, Internet-Draft, draft-ietf- netconf-keystore-35, 16 March 2024, . [I-D.ietf-netconf-tls-client-server] Watsen, K., "YANG Groupings for TLS Clients and TLS Servers", Work in Progress, Internet-Draft, draft-ietf- netconf-tls-client-server-41, 16 March 2024, . [I-D.ietf-netconf-trust-anchors] Watsen, K., "A YANG Data Model for a Truststore", Work in Progress, Internet-Draft, draft-ietf-netconf-trust- anchors-28, 16 March 2024, . [I-D.ietf-opsawg-tacacs-tls13] Dahm, T., Heasley, J., dcmgash@cisco.com, and A. Ota, "Terminal Access Controller Access-Control System Plus (TACACS+) over TLS 1.3", Work in Progress, Internet-Draft, draft-ietf-opsawg-tacacs-tls13-10, 22 May 2024, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . Boucadair Expires 29 November 2024 [Page 21] Internet-Draft YANG for TACACS+ over TLS May 2024 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, . [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, . [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, . [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, . [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013, . [RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for System Management", RFC 7317, DOI 10.17487/RFC7317, August 2014, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018, . [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . Boucadair Expires 29 November 2024 [Page 22] Internet-Draft YANG for TACACS+ over TLS May 2024 [RFC9105] Wu, B., Ed., Zheng, G., and M. Wang, Ed., "A YANG Data Model for Terminal Access Controller Access-Control System Plus (TACACS+)", RFC 9105, DOI 10.17487/RFC9105, August 2021, . [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, . [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, . 7.2. Informative References [I-D.ietf-netmod-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-11, 18 April 2024, . [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, . [RFC8907] Dahm, T., Ota, A., Medway Gash, D.C., Carrel, D., and L. Grant, "The Terminal Access Controller Access-Control System Plus (TACACS+) Protocol", RFC 8907, DOI 10.17487/RFC8907, September 2020, . Acknowledgments The document leverages data structures defined in [I-D.ietf-netconf-tls-client-server]. Author's Address Mohamed Boucadair (editor) Orange Email: mohamed.boucadair@orange.com Boucadair Expires 29 November 2024 [Page 23]