Internet DRAFT - draft-ietf-opsawg-tacacs-tls13
draft-ietf-opsawg-tacacs-tls13
Operations and Management Area Working Group T. Dahm
Internet-Draft
Updates: RFC8907 (if approved) D. Gash
Intended status: Standards Track Cisco Systems, Inc.
Expires: 26 July 2024 A. Ota
J. Heasley
NTT
23 January 2024
TACACS+ TLS 1.3
draft-ietf-opsawg-tacacs-tls13-05
Abstract
The TACACS+ Protocol [RFC8907] provides device administration for
routers, network access servers and other networked computing devices
via one or more centralized servers. This document, a companion to
the TACACS+ protocol [RFC8907], adds Transport Layer Security
(currently defined by TLS 1.3 [RFC8446]) support and obsoletes former
inferior security mechanisms.
Requirements 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
[BCP14] when, and only when, they appear in all capitals, as shown
here.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 July 2024.
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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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Technical Definitions . . . . . . . . . . . . . . . . . . . . 3
2.1. Obfuscation . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Non-TLS Connection . . . . . . . . . . . . . . . . . . . 3
2.3. TLS Connection . . . . . . . . . . . . . . . . . . . . . 3
2.4. TACACS+ Server . . . . . . . . . . . . . . . . . . . . . 4
2.5. Peer . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. TACACS+ over TLS . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Well-Known TCP/IP Port . . . . . . . . . . . . . . . . . 4
3.2. TLS Connection . . . . . . . . . . . . . . . . . . . . . 5
3.2.1. Cipher Requirements . . . . . . . . . . . . . . . . . 5
3.2.2. TLS Authentication . . . . . . . . . . . . . . . . . 5
3.3. TLS Identification . . . . . . . . . . . . . . . . . . . 6
4. Obsolescence of TACACS+ Obfuscation . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5.1. TLS . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1.1. TLS Use . . . . . . . . . . . . . . . . . . . . . . . 8
5.1.2. TLS 0-RTT . . . . . . . . . . . . . . . . . . . . . . 8
5.1.3. TLS Options . . . . . . . . . . . . . . . . . . . . . 8
5.1.4. Unreachable Certificate Authority (CA) . . . . . . . 9
5.1.5. TLS Server Name Indicator (SNI) . . . . . . . . . . . 9
5.2. TACACS+ Configuration . . . . . . . . . . . . . . . . . . 9
5.3. Well-Known TCP/IP Port . . . . . . . . . . . . . . . . . 10
6. Operator Considerations . . . . . . . . . . . . . . . . . . . 10
6.1. Migration . . . . . . . . . . . . . . . . . . . . . . . . 10
6.2. Maintaining Non-TLS TACACS+ Clients . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
9. Normative References . . . . . . . . . . . . . . . . . . . . 11
10. Informative References . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
The TACACS+ Protocol [RFC8907] provides device administration for
routers, network access servers and other networked computing devices
via one or more centralized servers. The protocol provides
authentication, authorization and accounting services for TACACS+
clients.
While the content of the protocol is highly sensitive, TACACS+ lacks
modern and/or effective confidentiality, integrity, and
authentication of the connection and network traffic between the
server and client. The existing mechanisms of TACACS+ are extremely
weak and the Security Considerations section of the TACACS+ Protocol
[RFC8907] adequately describes this.
To address these deficiencies, this document updates the TACACS+
Protocol [RFC8907] to use TLS 1.3 [RFC8446] authentication and
encryption, and obsoletes the use of its former mechanisms.
2. Technical Definitions
The Technical Definitions section of the TACACS+ Protocol [RFC8907]
is fully applicable here and will not be repeated. The following
terms are also used in this document.
2.1. Obfuscation
Inferior form of encryption used in TACACS+, referred to as
obfuscation in [RFC8907], Section 10.5.2 to indicate that it is not
encryption and is utterly insufficient.
2.2. Non-TLS Connection
This is another term for a connection defined in the historic TACACS+
Protocol [RFC8907]. It is a Connection without TLS and therefore
being plaintext or possibly using unsecure TACACS+ authentication and
obfuscation. The use of well-known TCP/IP Server Port 49 is
specified as the default for Non-TLS connections. Non-TLS
connections SHOULD NOT be used for new TACACS+ deployments.
2.3. TLS Connection
A TLS Connection is a TCP/IP connection with TLS authentication and
encryption used by TACACS+ for transport. The TLS Connection for
TACACS+ is always between one Client and one Server as defined in
TACACS+ Protocol [RFC8907].
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2.4. TACACS+ Server
In this document, we clarify that a TACACS+ server is an instance of
the Server as defined in [RFC8907], Section 3.2 that responds to
TACACS+ traffic on a specific port in a host, and does not refer to
the host itself. A host may have multiple TACACS+ servers installed,
listening to different ports.
2.5. Peer
In the context of a TLS Connection, the peer of a TACACS+ Client is
the Server, and the peer of a TACACS+ server is the Client.
Together, the ends of a TACACS+ Connection are referred as the peers.
3. TACACS+ over TLS
TACACS+ over TLS takes the protocol defined in TACACS+ Protocol
[RFC8907], removes the option for MD5 obfuscation, and specifies the
use of TLS (version 1.3 or later) for transport, to use a new well-
known default server port. The next sections provide further details
and guidance.
TLS is introduced into TACACS+ to fulfill the following requirements:
1. Confidentiality and Integrity: The MD5 Obfuscation specified in
the original protocol definition has been shown to be insecure
[RFC6151]. This prevents TACACS+ being used in a FIPS-140
compliant deployment. Securing TACACS+ protocol with TLS is
intended to provide confidentiality and integrity without
requiring the provision of a secured network.
2. Peer authentication: The authentication capabilities of TLS
replace the pre-shared keys of Obfuscation to authenticate Peers.
3.1. Well-Known TCP/IP Port
All data exchanged by TACACS+ Peers MUST be encrypted, including the
authentication of the Peers. Therefore, when a TCP connection is
established for the service, a TLS handshake begins immediately.
In order to ensure that the use of TLS and non-TLS TACACS+ traffic is
clearly differentiated (see Section 5.3, TACACS+ over TLS will follow
[RFC7605], where a different well-known system TCP/IP port is
assigned by IANA, port [TBD] (Section 7) with the service name [TBDN]
(Section 7), for TLS connections.
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TACACS+ TLS MAY be configured to use any other TCP port when required
by deployment specifics, but the implications in Section 5.3 should
still be considered.
3.2. TLS Connection
A TACACS+ Client initiates a TLS connection by making a TCP
connection to a configured Server on the TACACS+ TLS well-known port
([TBD]) (Section 3.1). Once the TCP connection is established, the
Client MUST immediately begin the TLS negotiation before sending any
TACACS+ protocol data.
Implementations MUST support TLS 1.3 [RFC8446] and MAY permit TLS 1.3
session resumption. If resumption is supported, the resumption
ticket_lifetime SHOULD be configurable, including a zero seconds
lifetime.
Once the TLS connection is established, the exchange of TACACS+ data
proceeds as normal, except that it is transmitted over TLS as TLS
application data and without TACACS+ obfuscation (see Section 4)
The connection persists until the Server or Client closes it. It
might be closed due to an error or at the conclusion of the TACACS+
Session. If Single Connection Mode has been negotiated, it might
remain open after a successful Session, until an error or an
inactivity timeout occurs. Why it closed has no bearing on TLS
resumption, unless closed by a TLS error, in which case the ticket
might be invalidated.
3.2.1. Cipher Requirements
Implementations MUST support the TLS 1.3 mandatory cipher suites (See
TLS 1.3 [RFC8446] Section 9.1). The cipher suites offered or
accepted SHOULD be configurable so that operators can adapt.
This document makes no cipher suite recommendations, but
recommendations can be found in the TLS Cipher Suites section of the
[TLSCSREC].
3.2.2. TLS Authentication
Implementations MUST support certificate-based TLS authentication and
certificate revocation bi-directionally for authentication, identity
verification and policy purposes. Certificate path verification as
described in Section 3.2.2.1 MUST be supported.
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If this succeeds, the authentication is successful and the connection
is permitted. Policy MAY impose further constraints upon the Peer,
allowing or denying the connection based on certificate fields or any
other parameters exposed by the implementation.
Unless disabled by configuration, a Peer MUST disconnect a Peer that
offers an invalid TLS Certificate.
Implementations MAY support TLS authentication with Pre-Shared Keys
(PSKs), also known as external PSKs in TLS 1.3, which are not
resumption PSKs. PSKs are considered out-of-scope for this document.
3.2.2.1. TLS Certificate Path Verification
Implementations MUST support certificate Path verification as
described in [RFC5280].
Because a Peer could be isolated from a remote Peer's Certificate
Authority (CA), implementations MUST support certificate chains (aka.
bundles or chains of trust), where the entire chain of the remote's
certificate is stored on the local Peer.
3.3. TLS Identification
In addition to authentication of TLS certificates, implementations
MUST support policy consideration of Peer-identifying certificate
fields and policy used to verify that the Peer is a valid source for
the received certificate and that it is permitted access to TACACS+.
Implementations MUST support either:
Network location based validation methods as described in [RFC5425],
Section 5.2.
or
Device Identity based validation methods where the peer’s identity is
used in the certificate subjectName. This is applicable in
deployments where the device securely supports an identity which is
shared with its peer. This approach allows a peer's network location
to be reconfigured without issuing a new client certificate. Only
the local server mapping needs to be updated.
Implementations SHOULD support the TLS Server Name Indication
extension ([RFC6066], Section 3). Policy can be applied to this
attribute and it can be useful for load balancing or multiplexing at
the server.
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4. Obsolescence of TACACS+ Obfuscation
The original draft of TACACS+ described the Obfuscation mechanism,
documented in [RFC5425], Section 5.2. It is insufficient for modern
purposes.
The introduction of TLS PSK, certificate Peer authentication, and TLS
encryption to TACACS+ replaces these former mechanisms and so
Obfuscation is hereby obsoleted. This section describes how the
TACACS+ client and servers MUST operate with regards to the
obfuscation mechanism.
Peers MUST NOT use Obfuscation with TLS.
A TACACS+ client initiating a TACACS+ TLS connection MUST set the
TAC_PLUS_UNENCRYPTED_FLAG bit, thereby asserting that Obfuscation is
not used for the Session. All subsequent packets MUST have the
TAC_PLUS_UNENCRYPTED_FLAG set.
A TACACS+ server that receives a packet with the
TAC_PLUS_UNENCRYPTED_FLAG not set (cleared) over a TLS connection,
MUST return an error of TAC_PLUS_AUTHEN_STATUS_ERROR,
TAC_PLUS_AUTHOR_STATUS_ERROR, or TAC_PLUS_ACCT_STATUS_ERROR as
appropriate for the TACACS+ message type, with the
TAC_PLUS_UNENCRYPTED_FLAG set, and terminate the Session. This
behavior corresponds to that defined in RFC8907 Section 4.5. Data
Obfuscation [RFC8907] for TAC_PLUS_UNENCRYPTED_FLAG or key
mismatches.
A TACACS+ client that receives a packet with the
TAC_PLUS_UNENCRYPTED_FLAG not set (cleared), MUST terminate the
Session, and SHOULD log this error.
5. Security Considerations
5.1. TLS
This document improves the confidentiality, integrity, and
authentication of the connection and network traffic between TACACS+
Peers by adding TLS support.
Simply adding TLS support to the protocol does not guarantee the
protection of the server and clients. It is essential for the
operators and equipment vendors to adhere to the latest best
practices for ensuring the integrity of network devices and selecting
secure TLS key and encryption algorithms.
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[RFC9325]. offers substantial guidance for implementing protocols
that use TLS and their deployment. Those implementing and deploying
Secure TACACS+ must adhere to the recommendations relevant to TLS 1.3
outlined in [RFC9325], or its subsequent versions.
This document outlines additional restrictions permissible under
[RFC9325]. For example, any recommendations referring to TLS 1.2,
including the mandatory support, are not relevant for Secure TACACS+
as TLS 1.3 or above is mandated.
5.1.1. TLS Use
TLS encryption SHOULD be used in deployments where both the clients
and servers support it. TACACS+ servers that have TLS support MUST
NOT allow non-TLS connections from clients that do not support TLS,
because of the threat of downgrade attacks, as described in
Section 5.2. Instead, separate non-TLS TACACS+ servers can be set up
to cater for these clients.
Further, TLS TACACS+ servers and non-TLS TACACS+ servers SHOULD NOT
be deployed on the same host. Non-TLS connections would be better
served by deploying the required Non-TLS TACACS+ servers on separate
hosts.
It is NOT RECOMMENDED to deploy TACACS+ without TLS authentication
and encryption, including TLS using the NULL algorithm, except for
within test and debug environments. Also see [RFC3365].
5.1.2. TLS 0-RTT
TLS 1.3 resumption and PSK techniques make it possible to send Early
Data, aka. 0-RTT data, data that is sent before the TLS handshake
completes. Replay of this data is possible. Given the sensitivity
of TACACS+ data, a Client MUST NOT send data until the full TLS
handshake completes; that is, Clients MUST NOT send 0-RTT data and
Servers MAY abruptly disconnect Clients that do.
5.1.3. TLS Options
Implementors and operators SHOULD make use of the various RFCs to
determine which TLS versions and algorithms should be supported,
deprecated, obsoleted, or abandoned, in the absence of updates to
this document.
Recommendations in [RFC9325] Section 4, or any RFCs which obsolete
it, MUST be followed.
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Other useful examples are the TLS specifications themselves (TLS 1.3
[RFC8446]), which prescribes mandatory support in Section 9, and TLS
Recommendations [RFC7525].
5.1.4. Unreachable Certificate Authority (CA)
Operators SHOULD be cognizant of the potential of Server and/or
Client isolation from their Peer's CA by network failures. Isolation
from a public key certificate's CA will cause the verification of the
certificate to fail and thus TLS authentication of the Peer to fail.
Operators SHOULD consider loading certificate chains on devices and
servers to avoid this failure.
Certificate caching and Raw Public Keys [RFC7250] are other methods
to help address this, but both are out of scope for this document.
Certificate fingerprints are another option.
5.1.5. TLS Server Name Indicator (SNI)
Operators SHOULD be aware that the TLS SNI extension is part of the
TLS client hello, and is therefore subject to eavesdropping. Also
see [RFC6066], Section 11.1.
If TLS Encrypted Client Hello becomes standardized and applicable to
TLS 1.3, then it SHOULD be included in Secure TACACS+ implementation.
5.2. TACACS+ Configuration
Implementors MUST ensure that the configuration scheme introduced for
enabling TLS is straightforward and leaves no room for ambiguity
regarding whether TLS or non-TLS will be used between the TACACS+
client and the TACACS+ server.
This document introduces a separate port that TLS enabled TACACS+
servers will listen to. Where deployments have not overridden the
defaults explicitly, TACACS+ client implementations MUST use the
correct values:
* for non-TLS connection TACACS+: Port 49.
* for TLS connection TACACS+: (TBD).
Implementors MAY offer a single option for TACACS+ clients and
servers to disable all non-TLS TACACS+ operations. When enabled on a
TACACS+ server, it will not respond to any requests from non-TLS
TACACS+ client connections. When enabled on a TACACS+ client, it
will not establish any non-TLS TACACS+ server connections.
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5.3. Well-Known TCP/IP Port
A new port is considered appropriate and superior to a "STARTTLS"
command or other negotiation method because it allows:
* ease of blocking the unobfuscated or obfuscated connections by the
TCP/IP port number,
* passive Intrusion Detection Systems (IDSs) monitoring the
unobfuscated to be unaffected by the introduction of TLS,
* avoidance of Man in the Middle (MitM) attacks that can interfere
with STARTTLS,
* and helps prevent the accidental exposure of sensitive information
due to misconfiguration.
However, co-existence of inferior authentication and obfuscated,
whether an Non-TLS connection or deprecated parts that compose TLS,
also presents opportunity for down-grade attacks. Causing failure of
connections to the TLS-enabled service or the negotiation of shared
algorithm support are two such down-grade attacks.
The simplest way to address exposure from Non-TLS connection methods
is to refuse Non-TLS connections at the server entirely, perhaps
using separate servers for Non-TLS connections and TLS.
Another approach is mutual configuration that requires TLS. Clients
and Servers SHOULD support configuration that requires Peers,
globally and individually, use TLS. Furthermore, Peers SHOULD be
configurable to limit offered or recognized TLS versions and
algorithms to those recommended by standards bodies and implementers.
6. Operator Considerations
Operational and deployment considerations are spread throughout the
document. While avoiding repetition, it is useful for the impatient
to direct particular attention to Section 5.2 and Section 5.1.5.
However, it is important that the entire Section 5 is observed.
6.1. Migration
In section 5.2, it is mentioned that for an optimal deployment of TLS
TACACS+, TLS should be universally applied throughout the deployment.
However, during the migration process from a non-TLS TACACS+
deployment, operators may need to support both TLS and Non-TLS
TACACS+ servers. This migration phase allows operators to gradually
transition their deployments from an insecure state to a more secure
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one, but it is important to note that it is vulnerable to downgrade
attacks. Therefore, the migration phase should be considered
insecure until it is fully completed. To mitigate this hazard:
* the period where any client is configured with both TLS and non-
TLS servers SHOULD be minimized.
* the operator MUST consider the impact of mixed TLS and Non-TLS on
security.
6.2. Maintaining Non-TLS TACACS+ Clients
Some TACACS+ client devices in a deployment may not implement TLS.
These devices will require access to Non-TLS TACACS+ servers.
Operators MUST follow the recommendation of section Section 5.1.1 and
deploy separate TACACS+ servers for these Non-TLS clients from those
used for the TLS clients.
7. IANA Considerations
The authors request that, when this draft is accepted by the working
group, the OPSAWG Chairs submit a request to IANA for an early
allocation, per [RFC4020] and [RFC6335], of a new well-known system
TCP/IP port number for the service name "tacacss" (referenced in this
document also as "TACACS+ TLS well-known port ([TBD])"), described as
"TACACS+ over TLS". The service name "tacacss" follows the common
practice of appending an "s" to the name given to the non-TLS well-
known port name. This allocation is justified in Section 5.3.
RFC EDITOR: this port number should replace "[TBD]" and the service
name should replace "[TBDN]" within this document.
8. Acknowledgments
The author(s) would like to thank Russ Housley, Steven M. Bellovin,
Stephen Farrell, Alan DeKok, Warren Kumari, and Tom Petch for their
support, insightful review, and/or comments. [RFC5425] was also used
as a basis for the approach to TLS.
9. Normative References
[BCP14] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, May 2017.
<https://www.rfc-editor.org/bcp/bcp14.txt>
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[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>.
[RFC5425] Miao, F., Ed., Ma, Y., Ed., and J. Salowey, Ed.,
"Transport Layer Security (TLS) Transport Mapping for
Syslog", RFC 5425, DOI 10.17487/RFC5425, March 2009,
<https://www.rfc-editor.org/info/rfc5425>.
[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extensions: Extension Definitions", RFC 6066,
DOI 10.17487/RFC6066, January 2011,
<https://www.rfc-editor.org/info/rfc6066>.
[RFC6151] Turner, S. and L. Chen, "Updated Security Considerations
for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
RFC 6151, DOI 10.17487/RFC6151, March 2011,
<https://www.rfc-editor.org/info/rfc6151>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/info/rfc7301>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", RFC 7525, DOI 10.17487/RFC7525, May 2015,
<https://www.rfc-editor.org/info/rfc7525>.
[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>.
[RFC8773] Housley, R., "TLS 1.3 Extension for Certificate-Based
Authentication with an External Pre-Shared Key", RFC 8773,
DOI 10.17487/RFC8773, March 2020,
<https://www.rfc-editor.org/info/rfc8773>.
[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,
<https://www.rfc-editor.org/info/rfc8907>.
10. Informative References
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[I-D.ietf-tls-external-psk-guidance]
Housley, R., Hoyland, J., Sethi, M., and C. A. Wood,
"Guidance for External Pre-Shared Key (PSK) Usage in TLS",
Work in Progress, Internet-Draft, draft-ietf-tls-external-
psk-guidance-06, 4 February 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-tls-
external-psk-guidance-06>.
[RFC3365] Schiller, J., "Strong Security Requirements for Internet
Engineering Task Force Standard Protocols", BCP 61,
RFC 3365, DOI 10.17487/RFC3365, August 2002,
<https://www.rfc-editor.org/info/rfc3365>.
[RFC4020] Kompella, K. and A. Zinin, "Early IANA Allocation of
Standards Track Code Points", RFC 4020,
DOI 10.17487/RFC4020, February 2005,
<https://www.rfc-editor.org/info/rfc4020>.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011,
<https://www.rfc-editor.org/info/rfc6335>.
[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>.
[RFC7605] Touch, J., "Recommendations on Using Assigned Transport
Port Numbers", BCP 165, RFC 7605, DOI 10.17487/RFC7605,
August 2015, <https://www.rfc-editor.org/info/rfc7605>.
[RFC9325] Sheffer, Y., Saint-Andre, P., and T. Fossati,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, November
2022, <https://www.rfc-editor.org/info/rfc9325>.
[TLSCSREC] IANA, "Transport Layer Security (TLS) Parameters",
<https://www.iana.org/assignments/tls-parameters/tls-
parameters.xhtml#tls-parameters-4>.
Authors' Addresses
Thorsten Dahm
Dahm, et al. Expires 26 July 2024 [Page 13]
Internet-Draft TACACS+ TLS 1.3 January 2024
Email: thorsten.dahm@gmail.com
Douglas Gash
Cisco Systems, Inc.
Email: dcmgash@cisco.com
Andrej Ota
Email: andrej@ota.si
John Heasley
NTT
Email: heas@shrubbery.net
Dahm, et al. Expires 26 July 2024 [Page 14]
