Terminal Access Controller Access-Control System Plus over TLS 1.3 (TACACS+ over TLS)
draft-ietf-opsawg-tacacs-tls13-24

Received changes through RFC Editor sync (changed state to RFC, created became rfc relationship between draft-ietf-opsawg-tacacs-tls13 and RFC 9887, changed IESG state to RFC Published)

[Ballot comment]
Thanks for the work on this document and updating TACACS+ for TLS. This is a much needed security upgrade for the widely used protocol.

Thanks for clarification on the history of why TACACS+ was developed as informational document to help clear my DISCUSS.

I am still wondering whether informational status is not more appropriate for this document as well.

[Ballot comment]
Thanks for a clear document. I just have one comment:

        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 Section 11.1 of [RFC6066].

I am not sure why this really matters? I presume the name is already in
public DNS and/or reverse DNS and is probably already well known? It
will be using a new tacacss well-known port so the name isn't needed
to leak information that the connection is tacacs.

Also, if it mattered, since the server is likely dedicated to this
purpose, why use SNI? One could just not use it, as the target server
doesn't need to vhost demux the HTTPS request anyway? And finally,
one could use ECH to protect against SNI sniffing, if it really mattered.

[Ballot comment]
# Gunter Van de Velde, RTG AD, comments for draft-ietf-opsawg-tacacs-tls13-23

# The line numbers used are rendered from IETF idnits tool: https://author-tools.ietf.org/api/idnits?url=https://www.ietf.org/archive/id/draft-ietf-opsawg-tacacs-tls13-23.txt

# This is a great write-up and needed extension to TACACS+

# I noted some non-blocking observations in the text that follows. Mostly idnits and clarifications.

# Detailed Review
# ===============

16 Abstract
17
18   The Terminal Access Controller Access-Control System Plus (TACACS+)
19   protocol provides device administration for routers, network access
20   servers, and other networked computing devices via one or more
21   centralized TACACS+ servers.  This document adds Transport Layer
22   Security (TLS 1.3) support to TACACS+ and obsoletes former inferior
23   security mechanisms.
24
25   This document updates RFC 8907.

GV> What about the following textblob alternative:

"
This document specifies the use of Transport Layer Security (TLS) version 1.3 to secure the communication channel between a TACACS+ client and server. TACACS+ is a protocol used for Authentication, Authorization, and Accounting (AAA) in networked environments. The original TACACS+ protocol, defined in RFC 8907, does not mandate the use of encryption or secure transport. This specification defines a profile for using TLS 1.3 with TACACS+, including guidance on authentication, connection establishment, and operational considerations. The goal is to enhance the confidentiality, integrity, and authenticity of TACACS+ traffic, aligning the protocol with modern security best practices.

This document updates RFC 8907.
"

183 3.1.  Separating TLS Connections
184
185   All data exchanged by TACACS+ peers MUST be encrypted, including the
186   mutual authentication of the peers.  Therefore, when a TCP connection
187   is established for the service, a TLS handshake begins immediately.

GV> This reads like a storm of energy of change and leaves no room for introduction. The text states "peers MUST be encrypted". While true when supporting this RFC-to-be, it was not the situation before this RFC-to-be. Maybe mention in the text that it MUST be supported when this RFC-to-be is supported.

189   To ensure separation of TACACS+ traffic that uses TLS from that which
190   does not (Section 5.3), TLS TACACS+ servers MUST be deployed on a
191   separate TCP/IP port number from Non-TLS TACACS+ servers (preferably
192   on a separate host, as recommended in Section 5.1.1).  Because of the
193   widespread use of default port number settings in numerous existing
194   TACACS+ client configurations, a well-known system TCP/IP port number
195   is assigned: the designated port number is [TBD] (Section 7) with the
196   service name tacacss (Section 7).  This ensures that the client can
197   separate TLS and Non-TLS traffic even where default port numbers are
198   omitted from its TACACS+ server connection configuration.
199
200   Under exceptional circumstances, this document permits any other TCP
201   port number to be configured when required by deployment specifics,
202   but the implications in Section 5.3 have to be considered by

GV> What about the following alternative textblob:

"
To ensure clear separation between TACACS+ traffic using TLS and that which does not (see Section 5.3), servers supporting TACACS+ over TLS MUST listen on a TCP/IP port distinct from that used by non-TLS TACACS+ servers. Where feasible, it is further RECOMMENDED to deploy the TLS and non-TLS services on separate hosts, as discussed in Section 5.1.1.

Given the prevalence of default port usage in existing TACACS+ client implementations, this specification assigns a well-known TCP port number for TACACS+ over TLS: [TBD], with the associated service name "tacacss" (see Section 7). This allows clients to unambiguously distinguish between TLS and non-TLS connections, even in the absence of an explicitly configured port number.

While the use of the designated port is strongly encouraged, deployments with specific requirements MAY use alternative TCP port numbers. In such cases, operators must carefully consider the operational implications described in Section 5.3.
"

213   TLS 1.3 [RFC8446] must be used for transport, though it is expected
214   that TACACS+ as described in this document will work with future
215   versions of TLS.  Earlier versions of TLS MUST NOT be used.

GV> Would it be beneficial to state that "minimum TLS 1.3 MUST be used for transport ..."?

217   Once the TLS connection is established, the exchange of TACACS+ data
218   proceeds as defined in [RFC8907], except that it is transmitted over
219   TLS as TLS application data and without TACACS+ obfuscation
220   (Section 4).

GV> What about:

"
Once the TLS connection has been successfully established, the exchange of TACACS+ data SHALL proceed in accordance with the procedures defined in [RFC8907]. However, all TACACS+ messages SHALL be transmitted as TLS application data. The TACACS+ obfuscation mechanism defined in [RFC8907] MUST NOT be applied when operating over TLS (see Section 4)
"

225   negotiated, when an inactivity timeout occurs.  Why it closed has no
226   bearing on TLS resumption, unless closed by a TLS error, in which
227   case the ticket might be invalidated.

GV> What is meant with "ticket"?

229   TACACS+ connections are not long-lived.  Non 'Single Connection Mode'
230   (Section 4.3 of [RFC8907]) connections are closed as soon as the
231   TACACS+ session completes.  Single Connection Mode connections are
232   longer lived, but even these are timed out and closed after a short
233   period of inactivity.  For this reason, keepalives are not required
234   to be supported.

GV> What about:

"
TACACS+ connections are generally not long-lived. For connections not operating in Single Connection Mode (as defined in Section 4.3 of [RFC8907]), the TCP session SHALL be closed upon completion of the associated TACACS+ session. Connections operating in Single Connection Mode MAY persist for a longer duration but are typically subject to timeout and closure after a brief period of inactivity. Consequently, support for transport-layer keepalive mechanisms is NOT REQUIRED.
"

421   The introduction of TLS PSK, certificate peer authentication, and TLS
422   encryption to TACACS+ replaces these former mechanisms and so
423   obfuscation is hereby obsoleted.

GV>  Is TLS PSK in this document not documented after the TLS Encryption? Maybe follow order in the above phrase to be conmsistent with the documentation in this RFC-to-be for readability?

502   completes.  Replay of this data is a risk.  Given the sensitivity of
503   TACACS+ data, clients MUST NOT send data until the full TLS handshake
504   completes; that is, clients MUST NOT send 0-RTT data and TLS TACACS+
505   servers MUST abruptly disconnect clients that do.

GV> Beyond the abruptly disconnect, is an operational logging recommended?


Many thanks for this document,
Gunter Van de Velde,
Routing AD

[Ballot comment]
FWIW, the approach followed in this spec is what was agreed with the IESG at the time of publication of RFC 8907 and which is captured in the note sent by Warren to the WG to act upon (2021): https://mailarchive.ietf.org/arch/msg/opsawg/IPNhvGyhDAawsavqRUHIliCr4xk/, especially this part:

" When we wrote this, it was with the understanding that we'd first puslish how TACACS+ currently works, and then a second document which, AFAIR, would basically say "... and now just run this over TLS, K,  thanks, done". "

[Ballot comment]
# Gunter Van de Velde, RTG AD, comments for draft-ietf-opsawg-tacacs-tls13-23

# The line numbers used are rendered from IETF idnits tool: https://author-tools.ietf.org/api/idnits?url=https://www.ietf.org/archive/id/draft-ietf-opsawg-tacacs-tls13-23.txt

# This is a great write-up and needed extension to TACACS+

# I noted some non-blocking observations in the text that follows. Mostly idnits and clarifications.

# A support the DISCUSS from Ketan

# Detailed Review
# ===============

16 Abstract
17
18   The Terminal Access Controller Access-Control System Plus (TACACS+)
19   protocol provides device administration for routers, network access
20   servers, and other networked computing devices via one or more
21   centralized TACACS+ servers.  This document adds Transport Layer
22   Security (TLS 1.3) support to TACACS+ and obsoletes former inferior
23   security mechanisms.
24
25   This document updates RFC 8907.

GV> What about the following textblob alternative:

"
This document specifies the use of Transport Layer Security (TLS) version 1.3 to secure the communication channel between a TACACS+ client and server. TACACS+ is a protocol used for Authentication, Authorization, and Accounting (AAA) in networked environments. The original TACACS+ protocol, defined in RFC 8907, does not mandate the use of encryption or secure transport. This specification defines a profile for using TLS 1.3 with TACACS+, including guidance on authentication, connection establishment, and operational considerations. The goal is to enhance the confidentiality, integrity, and authenticity of TACACS+ traffic, aligning the protocol with modern security best practices.

This document updates RFC 8907.
"

183 3.1.  Separating TLS Connections
184
185   All data exchanged by TACACS+ peers MUST be encrypted, including the
186   mutual authentication of the peers.  Therefore, when a TCP connection
187   is established for the service, a TLS handshake begins immediately.

GV> This reads like a storm of energy of change and leaves no room for introduction. The text states "peers MUST be encrypted". While true when supporting this RFC-to-be, it was not the situation before this RFC-to-be. Maybe mention in the text that it MUST be supported when this RFC-to-be is supported.

189   To ensure separation of TACACS+ traffic that uses TLS from that which
190   does not (Section 5.3), TLS TACACS+ servers MUST be deployed on a
191   separate TCP/IP port number from Non-TLS TACACS+ servers (preferably
192   on a separate host, as recommended in Section 5.1.1).  Because of the
193   widespread use of default port number settings in numerous existing
194   TACACS+ client configurations, a well-known system TCP/IP port number
195   is assigned: the designated port number is [TBD] (Section 7) with the
196   service name tacacss (Section 7).  This ensures that the client can
197   separate TLS and Non-TLS traffic even where default port numbers are
198   omitted from its TACACS+ server connection configuration.
199
200   Under exceptional circumstances, this document permits any other TCP
201   port number to be configured when required by deployment specifics,
202   but the implications in Section 5.3 have to be considered by

GV> What about the following alternative textblob:

"
To ensure clear separation between TACACS+ traffic using TLS and that which does not (see Section 5.3), servers supporting TACACS+ over TLS MUST listen on a TCP/IP port distinct from that used by non-TLS TACACS+ servers. Where feasible, it is further RECOMMENDED to deploy the TLS and non-TLS services on separate hosts, as discussed in Section 5.1.1.

Given the prevalence of default port usage in existing TACACS+ client implementations, this specification assigns a well-known TCP port number for TACACS+ over TLS: [TBD], with the associated service name "tacacss" (see Section 7). This allows clients to unambiguously distinguish between TLS and non-TLS connections, even in the absence of an explicitly configured port number.

While the use of the designated port is strongly encouraged, deployments with specific requirements MAY use alternative TCP port numbers. In such cases, operators must carefully consider the operational implications described in Section 5.3.
"

213   TLS 1.3 [RFC8446] must be used for transport, though it is expected
214   that TACACS+ as described in this document will work with future
215   versions of TLS.  Earlier versions of TLS MUST NOT be used.

GV> Would it be beneficial to state that "minimum TLS 1.3 MUST be used for transport ..."?

217   Once the TLS connection is established, the exchange of TACACS+ data
218   proceeds as defined in [RFC8907], except that it is transmitted over
219   TLS as TLS application data and without TACACS+ obfuscation
220   (Section 4).

GV> What about:

"
Once the TLS connection has been successfully established, the exchange of TACACS+ data SHALL proceed in accordance with the procedures defined in [RFC8907]. However, all TACACS+ messages SHALL be transmitted as TLS application data. The TACACS+ obfuscation mechanism defined in [RFC8907] MUST NOT be applied when operating over TLS (see Section 4)
"

225   negotiated, when an inactivity timeout occurs.  Why it closed has no
226   bearing on TLS resumption, unless closed by a TLS error, in which
227   case the ticket might be invalidated.

GV> What is meant with "ticket"?

229   TACACS+ connections are not long-lived.  Non 'Single Connection Mode'
230   (Section 4.3 of [RFC8907]) connections are closed as soon as the
231   TACACS+ session completes.  Single Connection Mode connections are
232   longer lived, but even these are timed out and closed after a short
233   period of inactivity.  For this reason, keepalives are not required
234   to be supported.

GV> What about:

"
TACACS+ connections are generally not long-lived. For connections not operating in Single Connection Mode (as defined in Section 4.3 of [RFC8907]), the TCP session SHALL be closed upon completion of the associated TACACS+ session. Connections operating in Single Connection Mode MAY persist for a longer duration but are typically subject to timeout and closure after a brief period of inactivity. Consequently, support for transport-layer keepalive mechanisms is NOT REQUIRED.
"

421   The introduction of TLS PSK, certificate peer authentication, and TLS
422   encryption to TACACS+ replaces these former mechanisms and so
423   obfuscation is hereby obsoleted.

GV>  Is TLS PSK in this document not documented after the TLS Encryption? Maybe follow order in the above phrase to be conmsistent with the documentation in this RFC-to-be for readability?

502   completes.  Replay of this data is a risk.  Given the sensitivity of
503   TACACS+ data, clients MUST NOT send data until the full TLS handshake
504   completes; that is, clients MUST NOT send 0-RTT data and TLS TACACS+
505   servers MUST abruptly disconnect clients that do.

GV> Beyond the abruptly disconnect, is an operational logging recommended?


Many thanks for this document,
Gunter Van de Velde,
Routing AD

[Ballot comment]

I support Ketan's discuss.  This protocol is in wide use, it would be useful to have the whole protocol be PS.

Thanks to Russ Housley for their secdir review.

Section 3, last sentence:  This draft is almost in the RFC Editor's queue.  It would be better if it could be a normative reference, since it is exactly what you are trying to specify here.

Section 3.4.1:  Sometimes these (both cert path validation and revocation checking) can be quite hard.  Many implementations of TLS allow a bypass in the case of network latency issues.  And while it pains me to say this as 'a PKI person', you may need to consider whether there needs to be an allowance for a bypass. What happens if there are network issues blocking chains or OCSP? 

Section 5.1.2:  There is an 'early data extension' that the client could include to enable the ability to send early data.  Perhaps the statement 'A TLS client or server MUST NOT include the "early_data" extension. See Section 2.3 and 4.2.10 of [RFC8446] for security concerns.' or something similar could be added.

Section 5.1.5:  'subject to eavesdropping' because SNI is sent in the clear in the Client Hello?  Would it be more direct to say something like, 'the TLS SNI extension is part of the TLS client hello, which is sent in cleartext and is, therefore...'  That might make for an awkward sentence, which could be split into two sentences. 

Section 5.2:  Nit:  just be sure the (TBD) is properly flagged for IANA.

Section 5.3:  I'm not sure it is necessary to throw STARTTLS 'under the bus' as it were.  The point can be made w/out it (especially since no reference to STARTTLS is supplied).  I'd be happy to help with the re-write.  [https://en.wikipedia.org/wiki/Throw_under_the_bus]

[Ballot comment]

# Éric Vyncke, INT AD, comments for draft-ietf-opsawg-tacacs-tls13-23
CC @evyncke

Thank you for the work put into this document.

Please find below some non-blocking COMMENT points/nits (replies would be appreciated even if only for my own education).

Special thanks to Joe Clarke for the shepherd's detailed write-up including the WG consensus *and* the justification of the intended status especially the relationship to the informational RFC 8907.

I hope that this review helps to improve the document,

Regards,

-éric

## COMMENTS (non-blocking)

### Header

The header part is missing the draft name (not critical at this stage).

### QUIC

At least, some justifications why TLS was preferred to QUIC or HTTPS would be welcome.

### Section 3.1

I was unaware that the TLS handshake can be done not immediately after the TCP handshake as hinted by `Therefore, when a TCP connection is established for the service, a TLS handshake begins immediately.` or should this sentence be removed ?

s/separate TCP/IP port number /separate TCP port/

### Section 3.2

s/in which case the ticket might be invalidated/in which case the *session resumption* ticket might be invalidated/

I am not a security expert, but s/might/SHOULD/ seems more appropriate with an explanation *when* it can be kept.


### Section 3.4.1

When can the "SHOULD" by bypassed in `TLS Cached Information Extension [RFC7924] SHOULD be implemented.` ?

### Section 7

Unsure how to read `IANA (has allocated) is requested ` as the IANA has not yet allocated a port number (you may want to suggest a value).

### Operational considerations

Should the impact of the use of mutual TLS authentication be described ? Notably the provisioning of certs to all peers.

[Ballot discuss]
Thanks for the work on this document and updating TACAS+ for TLS.

I have read the shepherd writeup regarding the proposed PS status for this. Since the security issues were the reason why the base TACAS+ document was downgraded from PS and this document is fixing that, I would like to discuss with the authors/WG why they did not do this work as a BIS such that the base TACAS+ would also get elevated to PS status?

Given its use, I would have thought updating TACAS+ to PS with this fix would be of help to the community.

[Ballot comment]
Thanks to Russ Housley for the General Area Review Team (Gen-ART) review
(https://mailarchive.ietf.org/arch/msg/gen-art/cNyvkP_-A4zahKP-Ln_-DgozZzg).

In general, found the document easy to read. I have some minor COMMENT and NIT.

-------------------------------------------------------------------------------
COMMENT
-------------------------------------------------------------------------------

No reference entries found for these items, which were mentioned in the text:
[draft-ietf-radext-tls-psk] and [I-D.ietf-uta-require-tls13].

Found terminology that should be reviewed for inclusivity; see
https://www.rfc-editor.org/part2/#inclusive_language for background and more
guidance:

* Term "man"; alternatives might be "individual", "people", "person"

-------------------------------------------------------------------------------
NIT
-------------------------------------------------------------------------------

All comments below are about very minor potential issues that you may choose to
address in some way - or ignore - as you see fit. Some were flagged by
automated tools (via https://github.com/larseggert/ietf-reviewtool), so there
will likely be some false positives. There is no need to let me know what you
did with these suggestions.

Section 3.4, paragraph 1
>    Deploying TLS certificate-based uthentication correctly will
>    considerably improve the security of TACACS+ deployments.  It is
>    essential for implementers and operators to understand the
>    implications of a TLS certificate-based authentication solution,
>    including the correct handling of certificates, Certificate
>    Authorities (CAs), and all elements of TLS configuration.  For
>    guidance, start with [BCP195].

s/uthentication/authentication/

Section 5.1.6, paragraph 0
>    The use of wildcards in TLS server identities creates a single point
>    of failure: a compromised private key of a wildcard certificate
>    impacts all servers using it.  Their use MUST follow recommendations
>    of Section 7.1 of [RFC9525].  Operators MUST ensure that the wildcard
>    is limited to a subdomain dedicated solely to TLS TACACS+ servers.
>    Further, operators MUST ensure that the TLS TACACS+ servers covered
>    by a wildcard certificate MUST be impervious to redirection of
>    traffic to a different server (for example, due to MiTM attacks or
>    DNS cache poisoning).

Though expanded later, would prefer that MiTM is expanded here, as it is the first use of the acronym.

Uncited references: [TLSCSREC].

Section 3.6, paragraph 2
> lient and servers MUST operate with regards to the obfuscation mechanism. Pe
>                                ^^^^^^^^^^^^^^^
Use "in regard to", "with regard to", or more simply "regarding".

[Ballot comment]
# Andy Newton, ART AD, comments for draft-ietf-opsawg-tacacs-tls13-21
CC @anewton1998

* line numbers:
  - https://author-tools.ietf.org/api/idnits?url=https://www.ietf.org/archive/id/draft-ietf-opsawg-tacacs-tls13-21.txt&submitcheck=True

* comment syntax:
  - https://github.com/mnot/ietf-comments/blob/main/format.md

* "Handling Ballot Positions":
  - https://ietf.org/about/groups/iesg/statements/handling-ballot-positions/

Many thanks to Rich Salz for the ARTART review.

IESG/Authors/WG Chairs:

IANA has completed its review of draft-ietf-opsawg-tacacs-tls13-20. If any part of this review is inaccurate, please let us know.

IANA understands that, upon approval of this document, there is a single action which we must complete.

A single new port number is to be registered in the Service Name and Transport Protocol Port Number Registry located at

https://www.iana.org/assignments/service-names-port-numbers/

as follows:

Service Name: tacacss
Port Number: [ TBD-at-Registration ]
Transport Protocol: TCP
Assignee: IESG
Contact: IETF Chair
Description: TLS Secure Login Host Protocol (TACACSS)
Reference: [ RFC-to-be ]
Assignment Notes:

As this requests a registration in an Expert Review or Specification Required (see RFC 8126) registry, we will initiate the required Expert Review via a separate request. This review must be completed before the document's IANA state can be changed to "IANA OK."

NOTE: The action requested in this document will not be completed until the document has been approved for publication as an RFC. This message is meant only to confirm the action that will be performed.

For definitions of IANA review states, please see:

https://datatracker.ietf.org/help/state/draft/iana-review

Thank you,

David Dong
IANA Services Sr. Specialist

The following Last Call announcement was sent out (ends 2025-04-28):

From: The IESG
To: IETF-Announce
CC: draft-ietf-opsawg-tacacs-tls13@ietf.org, jclarke@cisco.com, mohamed.boucadair@orange.com, opsawg-chairs@ietf.org, opsawg@ietf.org
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (Terminal Access Controller Access-Control System Plus over TLS 1.3 (TACACS+ over TLS)) to Proposed Standard


The IESG has received a request from the Operations and Management Area
Working Group WG (opsawg) to consider the following document: - 'Terminal
Access Controller Access-Control System Plus over TLS 1.3
  (TACACS+ over TLS)'
  as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits final
comments on this action. Please send substantive comments to the
last-call@ietf.org mailing lists by 2025-04-28. Exceptionally, comments may
be sent to iesg@ietf.org instead. In either case, please retain the beginning
of the Subject line to allow automated sorting.

Abstract


  The Terminal Access Controller Access-Control System Plus (TACACS+)
  protocol provides device administration for routers, network access
  servers, and other networked computing devices via one or more
  centralized TACACS+ servers.  This document adds Transport Layer
  Security (TLS 1.3) support to TACACS+ and obsoletes former inferior
  security mechanisms.

  This document updates RFC 8907.





The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-opsawg-tacacs-tls13/



No IPR declarations have been submitted directly on this I-D.


The document contains these normative downward references.
See RFC 3967 for additional information:
    rfc8907: The Terminal Access Controller Access-Control System Plus (TACACS+) Protocol (Informational - Internet Engineering Task Force (IETF) stream)

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

The consensus represents the strong concurrence of a few individuals, with
others being silent.


2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

No controversy. The authors was responsive enough in tracking and processing all
Comments.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

No.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

Yes, at least an implementation was disclosed at
https://mailarchive.ietf.org/arch/msg/opsawg/XQ3nytQ-bnXmWcrcqZRMvcbQ3ok/

A plan to implement was also shared here:
https://mailarchive.ietf.org/arch/msg/opsawg/UOWVLRZab_02QzIqevRlS6-shrw/ 


## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

Yes. The document leverages BCPs and specifications developed in other WGs.
The document avoids specific/customized behaviors when possible and tried to maximize
factorization of existing behaviors. Also, in order to inherit future guidelines,
the document cites BCP195 instead of RFC 9325.

There were some areas where existing BCPs/RFCs do not provide sufficient implementation
details. The document inspired from other applications (e.g., draft-ietf-radext-tls-psk).
This is ACKed in the document.

Many iterations were needed to converge on the current level details. Thanks to the support
of experts such as Alan DeKok.

The development of the document revealed the need for global guidance (e.g., by UTA)
rather that each application relying on TLS specifies its own behavior  (e.g., Debugging TACACS+ over TLS).
See https://mailarchive.ietf.org/arch/msg/opsawg/RpstFYI1dVcLnOm9Hb_FjXmkmnE/ for more details
about what seems a plan.

See also below for the external reviews, including from UTA.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

N/A

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

N/A

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

N/A

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

Definitely. This is an over-due document. It is well-written and is technically solid.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

The WG actively sought early in the process to secure reviews from OPS, transport,
and security areas.

The WG also solicited UTA WG, with the WGLC circulated also in UTA:
  * https://mailarchive.ietf.org/arch/msg/uta/KmRofaCQU2OWNp8acXuGjDyoPng/

Also, the WG sought for experts reviews for the TLS part, particularly:

* Valery: https://mailarchive.ietf.org/arch/msg/opsawg/U3mPq3WlRF48blMmr2uCF80KLiI/
* Tiru: https://mailarchive.ietf.org/arch/msg/opsawg/lWIGe93NCcmUF7U1XUgQY0aqH5w/

All these reviews were adequately addressed by the authors.

No further reviews are needed.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

The document targets Proposed Standard. This is well-documented in both the front
page and Datatracker metadata.

This intended track is justified given the interoperability requirement to deploy
TACACS+TLS clients and servers. The document includes the requirement normative
behavior to ensure such interoperability.

Note that the document updates an Informational document (RFC 8907), though. However,
that is not a problem because the status of RFC 8907 was set on-purpose as Informational
at the time of publication to acknowledge that, although RFC 8907 specifies a protocol
and given its security limitations, the publication was granted to document the protocol
as widely deployed. The deal with the IESG at the time was that the WG will supplement
a PS that will fix these issues.
This document removes those security limitations and Proposed Standard is adequate.

12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

Yes.

  * Thorsten: https://mailarchive.ietf.org/arch/msg/opsawg/BKAFwpGB6guT0li2OXEkCw9lqDM/
  * John: https://mailarchive.ietf.org/arch/msg/opsawg/9ttUzCNXz-RdNpOyNZk6djwdiY8/ 
  * Doug: https://mailarchive.ietf.org/arch/msg/opsawg/sBuAyZjhQaf3MjgGsnwclG0Hh68/
  * Andrej: https://mailarchive.ietf.org/arch/msg/opsawg/wvz4aMxEuRJg7VPTtyGO6Nxk8Ck/

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

Yes, as evidenced by the replies to IPR polls.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

The following should be fixed:

  == Unused Reference: 'TLSCSREC' is defined on line 767, but no explicit
    reference was found in the text

  -- Obsolete informational reference (is this intentional?): RFC 4020
    (Obsoleted by RFC 7120)

I suggest to delete both entries.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

All references are well classified.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

N/A.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

Yes, RFC 8907. This normative dependency is unavoidable given that the document
Leverage the “legacy” TACACS+ and enhances it to be more secure by adding TLS.

Also, the document has a normative dependency on BCP195/RFC9325, which is not
in the downref. However, the registry should be fixed given existing normative
dependency on that RFC as evidenced by https://datatracker.ietf.org/doc/rfc9325/referencedby/.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

No. All normative references are published RFCs.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

This document will update RFC 8907. This is clearly indicated on the title
page, the abstract, and the introduction.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

The document requests IANA to register a well-known port number and a service
Name to TACACS+TLS. The target registry is clearly identified with a link
Included. Also, the required information to perform the registration is provided.

Note that the authors refers to RFC4020, but that reference can be removed as
no early allocation is requested here, but a permanent assignment.

The WG reached out early in the development process of this document with
The TSV directorate to specifically review this request. The assigned
Reviewer didn’t flag any concern and confirmed that the request is
justified (2024-05-05).

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

N/A. The document does not introduce any new registry.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://wiki.ietf.org/group/ops/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://wiki.ietf.org/group/iesg/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

The consensus represents the strong concurrence of a few individuals, with
others being silent.


2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

No controversy. The authors was responsive enough in tracking and processing all
Comments.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

No.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

Yes, at least an implementation was disclosed at
https://mailarchive.ietf.org/arch/msg/opsawg/XQ3nytQ-bnXmWcrcqZRMvcbQ3ok/

A plan to implement was also shared here:
https://mailarchive.ietf.org/arch/msg/opsawg/UOWVLRZab_02QzIqevRlS6-shrw/ 


## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

Yes. The document leverages BCPs and specifications developed in other WGs.
The document avoids specific/customized behaviors when possible and tried to maximize
factorization of existing behaviors. Also, in order to inherit future guidelines,
the document cites BCP195 instead of RFC 9325.

There were some areas where existing BCPs/RFCs do not provide sufficient implementation
details. The document inspired from other applications (e.g., draft-ietf-radext-tls-psk).
This is ACKed in the document.

Many iterations were needed to converge on the current level details. Thanks to the support
of experts such as Alan DeKok.

The development of the document revealed the need for global guidance (e.g., by UTA)
rather that each application relying on TLS specifies its own behavior  (e.g., Debugging TACACS+ over TLS).
See https://mailarchive.ietf.org/arch/msg/opsawg/RpstFYI1dVcLnOm9Hb_FjXmkmnE/ for more details
about what seems a plan.

See also below for the external reviews, including from UTA.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

N/A

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

N/A

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

N/A

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

Definitely. This is an over-due document. It is well-written and is technically solid.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

The WG actively sought early in the process to secure reviews from OPS, transport,
and security areas.

The WG also solicited UTA WG, with the WGLC circulated also in UTA:
  * https://mailarchive.ietf.org/arch/msg/uta/KmRofaCQU2OWNp8acXuGjDyoPng/

Also, the WG sought for experts reviews for the TLS part, particularly:

* Valery: https://mailarchive.ietf.org/arch/msg/opsawg/U3mPq3WlRF48blMmr2uCF80KLiI/
* Tiru: https://mailarchive.ietf.org/arch/msg/opsawg/lWIGe93NCcmUF7U1XUgQY0aqH5w/

All these reviews were adequately addressed by the authors.

No further reviews are needed.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

The document targets Proposed Standard. This is well-documented in both the front
page and Datatracker metadata.

This intended track is justified given the interoperability requirement to deploy
TACACS+TLS clients and servers. The document includes the requirement normative
behavior to ensure such interoperability.

Note that the document updates an Informational document (RFC 8907), though. However,
that is not a problem because the status of RFC 8907 was set on-purpose as Informational
at the time of publication to acknowledge that, although RFC 8907 specifies a protocol
and given its security limitations, the publication was granted to document the protocol
as widely deployed. The deal with the IESG at the time was that the WG will supplement
a PS that will fix these issues.
This document removes those security limitations and Proposed Standard is adequate.

12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

Yes.

  * Thorsten: https://mailarchive.ietf.org/arch/msg/opsawg/BKAFwpGB6guT0li2OXEkCw9lqDM/
  * John: https://mailarchive.ietf.org/arch/msg/opsawg/9ttUzCNXz-RdNpOyNZk6djwdiY8/ 
  * Doug: https://mailarchive.ietf.org/arch/msg/opsawg/sBuAyZjhQaf3MjgGsnwclG0Hh68/
  * Andrej: https://mailarchive.ietf.org/arch/msg/opsawg/wvz4aMxEuRJg7VPTtyGO6Nxk8Ck/

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

Yes, as evidenced by the replies to IPR polls.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

The following should be fixed:

  == Unused Reference: 'TLSCSREC' is defined on line 767, but no explicit
    reference was found in the text

  -- Obsolete informational reference (is this intentional?): RFC 4020
    (Obsoleted by RFC 7120)

I suggest to delete both entries.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

All references are well classified.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

N/A.

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

Yes, RFC 8907. This normative dependency is unavoidable given that the document
Leverage the “legacy” TACACS+ and enhances it to be more secure by adding TLS.

Also, the document has a normative dependency on BCP195/RFC9325, which is not
in the downref. However, the registry should be fixed given existing normative
dependency on that RFC as evidenced by https://datatracker.ietf.org/doc/rfc9325/referencedby/.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

No. All normative references are published RFCs.

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

This document will update RFC 8907. This is clearly indicated on the title
page, the abstract, and the introduction.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

The document requests IANA to register a well-known port number and a service
Name to TACACS+TLS. The target registry is clearly identified with a link
Included. Also, the required information to perform the registration is provided.

Note that the authors refers to RFC4020, but that reference can be removed as
no early allocation is requested here, but a permanent assignment.

The WG reached out early in the development process of this document with
The TSV directorate to specifically review this request. The assigned
Reviewer didn’t flag any concern and confirmed that the request is
justified (2024-05-05).

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

N/A. The document does not introduce any new registry.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://wiki.ietf.org/group/ops/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://wiki.ietf.org/group/iesg/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/

Based on comments from the working group and authors, we are going to hold this draft in the WG for now.  There is an outstanding question on external PSKs where more WG input is needed (the authors have proposed two choices on this front).  Additionally, we have some SEC DIR feedback pending.

Based on comments from the working group and authors, we are going to hold this draft in the WG for now.  There is an outstanding question on external PSKs where more WG input is needed (the authors have proposed two choices on this front).  Additionally, we have some SEC DIR feedback pending.