Operations and Management Area Working Group M. Boucadair, Ed. Internet-Draft Orange Intended status: Informational 6 November 2024 Expires: 10 May 2025 A YANG Model for Terminal Access Controller Access-Control System Plus (TACACS+) over TLS 1.3 draft-ietf-opsawg-secure-tacacs-yang-00 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-ietf-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 10 May 2025 [Page 1] Internet-Draft YANG for TACACS+ over TLS November 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 10 May 2025. 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 . . . . . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 7.2. Informative References . . . . . . . . . . . . . . . . . 9 Appendix A. Full Tree . . . . . . . . . . . . . . . . . . . . . 9 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10 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 10 May 2025 [Page 2] Internet-Draft YANG for TACACS+ over TLS November 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 10 May 2025 [Page 3] Internet-Draft YANG for TACACS+ over TLS November 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 abstract tree structure is shown below: {::include-fold ./trees/tree-overview.txt} The following data nodes are supported: 'client-credentials' and 'server-credentials': Defines a set credentials that can be globally provisioned and then referenced under specific servers. '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. Both explicit and reference are supported. 'server-authentication': Specifies how a client authenticates Boucadair Expires 10 May 2025 [Page 4] Internet-Draft YANG for TACACS+ over TLS November 2024 servers. Both explicit and reference are supported. 'hello-params': Controls TLS versions and cipher suites. 'keepalives': Providers a set of parameters for testing the aliveness of the server. 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" {::include-fold ./yang/ietf-system-secure-tacacs.yang} 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. 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: Boucadair Expires 10 May 2025 [Page 5] Internet-Draft YANG for TACACS+ over TLS November 2024 '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 7. References 7.1. Normative References Boucadair Expires 10 May 2025 [Page 6] Internet-Draft YANG for TACACS+ over TLS November 2024 [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-tls13-14, 16 October 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 10 May 2025 [Page 7] Internet-Draft YANG for TACACS+ over TLS November 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 10 May 2025 [Page 8] Internet-Draft YANG for TACACS+ over TLS November 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-20, 21 October 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, . Appendix A. Full Tree The full tree structure is shown below: {::include-fold ./trees/full-tree.txt} Acknowledgments The document leverages data structures defined in [I-D.ietf-netconf-tls-client-server]. Thanks to Bo Wu for the review and comments. Boucadair Expires 10 May 2025 [Page 9] Internet-Draft YANG for TACACS+ over TLS November 2024 Author's Address Mohamed Boucadair (editor) Orange Email: mohamed.boucadair@orange.com Boucadair Expires 10 May 2025 [Page 10]