Subject: [OPSAWG] Genart telechat review of draft-ietf-opsawg-tacacs-13

From: Stewart Bryant via Datatracker <[email-masked]>
Date: Mon, 13 May 2019 05:54:25 -0700

Reviewer: Stewart Bryant
Review result: Almost Ready

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Document: draft-ietf-opsawg-tacacs-13
Reviewer: Stewart Bryant
Review Date: 2019-05-13
IETF LC End Date: None
IESG Telechat date: 2019-05-16

Summary:

There are a number of issues called out below that need addressing before publication.

Someone needs to micro-check the text to make sure that all terms are defined and referenced.
I picked up a few, but there were a lot I did not have time to check.

Major issues:

SB> The IANA section should ask IANA to point to this RFC as a reference
SB> for port 49

============

   The first MD5 hash is generated by concatenating the session_id, the
   secret key, the version number and the sequence number and then
   running MD5 over that stream.  All of those input values are
   available in the packet header, except for the secret key which is a
   shared secret between the TACACS+ client and server.

SB> MD5 make a good checksum, but I am surprised to see it used in this
SB> application in a new protocol.

=============

   All TACACS+ packets begin with the following 12-byte header.  The
   header describes the remainder of the packet:

SB> If ever there was an error in a long term session, how
SB> how would you find in in the following packet structure?
SB> Presumably from an incorrect major version and sequence number?

SB> Some details on the error cases and the unconditional "safety"
SB> of the protocol would be useful.

==========

      TAC_PLUS_AUTHEN_TYPE_ASCII := 0x01

      TAC_PLUS_AUTHEN_TYPE_PAP := 0x02

      TAC_PLUS_AUTHEN_TYPE_CHAP := 0x03

      TAC_PLUS_AUTHEN_TYPE_ARAP := 0x04 (deprecated)

      TAC_PLUS_AUTHEN_TYPE_MSCHAP := 0x05

      TAC_PLUS_AUTHEN_TYPE_MSCHAPV2 := 0x06

SB> There are lots of lists similar to the above.
SB> I have not checked them all, but a number of the types 
SB> in this and subsequent parts of the design don't seem
SB> to be defined or have a definitive reference

===========

 The START packet MUST contain a username and the data
   field MUST contain the PAP ASCII password.  A PAP authentication only
   consists of a username and password RFC 1334 [RFC1334] . The REPLY
   from the server MUST be either a PASS, FAIL or ERROR.

SB> Should there note be a note that RFC1334 is obsolete?

===========

Minor issues:

The use of the term "packet" as a unit of data is confusing, since the protocol
is carried over TCP which is a streaming protocol.

They are really TACAS+ PDUs

=========

(For example, Cisco uses "tty10"
   to denote the tenth tty line and "Async10" to denote the tenth async
   interface).  
SB> Is it correct to quote a particular vendor in an RFC of this type?

========

      TAC_PLUS_PRIV_LVL_MAX := 0x0f

      TAC_PLUS_PRIV_LVL_ROOT := 0x0f

      TAC_PLUS_PRIV_LVL_USER := 0x01

      TAC_PLUS_PRIV_LVL_MIN := 0x00

SB> Where are these defined?

========
Nits/editorial comments:

      The normative description of Legacy features such as ARAP and
SB> ARAP not expanded anywhere in document.

=====

SB> telnet and rlogin need references

=====
   is the user is connected via ISDN or a POTS, 
SB> Are ISDN and POTS well known IETF terms?

=====

   It is not legal for an attribute name to contain either of the
   separators.  It is legal for attribute values to contain the
   separators.  
SB> Is "legal" the correct term here?

---

From: Alissa Cooper <[email-masked]>
Date: Wed, 15 May 2019 14:57:26 -0400

Stewart, thanks for your review. I have entered a DISCUSS ballot based on a couple of your points.

Alissa

> On May 13, 2019, at 8:54 AM, Stewart Bryant via Datatracker <[email-masked]> wrote:
> 
> Reviewer: Stewart Bryant
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