Re: [EXT] Re: [cti] Advertising a CSD version of STIX and TAXII

I want to re-iterate some comments in slack because I think this thread is mixing up two different things, and they are even all mixed up in the Github issue tracker:

(a) How to advertise what version of a CSD you support in a product, in your literature or whatever.

(b) How to say as a TAXII client what version(s) of CSD you support when you make a request to a TAXII server.

These are two completely different problem spaces, and I get the impression everyone is worrying about (b) when it is not even a problem. I get this impression because everyone keeps talking about "code" and "coders" and substrings and whatnot.

(b) is not a problem because HTTP already allows you to do this:

Accept: application/stix+json; version=2.1, application/stix+json; version=2.1CSD02

.. and the client will handle whichever it is given (and it will know what it is given via the response header). No need for substrings or code changes.

Note that no where in STIX or TAXII is there an "advertisement" of what versions you support. This is important. Clients ask for what they can consume, not the other way around.

-
Jason Keirstead
STSM, Product Architect, Security Intelligence, IBM Security Systems
www.ibm.com/security

"Things may come to those who wait, but only the things left by those who hustle." - Unknown

From: Allan Thomson <athomson@lookingglasscyber.com>
To: Chris Larsen <Chris_Larsen@symantec.com>, Mark Davidson <Mark.Davidson@nc4.com>, Bret Jordan <Bret_Jordan@symantec.com>, "cti@lists.oasis-open.org" <cti@lists.oasis-open.org>
Date: 03/01/2018 02:39 PM
Subject: Re: [cti] Advertising a CSD version of STIX and TAXII
Sent by: <cti@lists.oasis-open.org>

Agreed. To my point that it comes down to what the org cares about.

Allan

From: Chris Larsen <Chris_Larsen@symantec.com>
Date: Thursday, March 1, 2018 at 10:35 AM
To: Allan Thomson <athomson@lookingglasscyber.com>, Mark Davidson <Mark.Davidson@nc4.com>, Bret Jordan <Bret_Jordan@symantec.com>, "cti@lists.oasis-open.org" <cti@lists.oasis-open.org>
Subject: Re: [cti] Advertising a CSD version of STIX and TAXII

You still have to decide what to have your regex look for: exact or simply containing.

Chris Larsen

Architect, WebPulse Threat Research Lab

Symantec

From: Allan Thomson <athomson@lookingglasscyber.com>
Sent: Thursday, March 1, 2018 11:28:32 AM
To: Chris Larsen; Mark Davidson; Bret Jordan; cti@lists.oasis-open.org
Subject: Re: [cti] Advertising a CSD version of STIX and TAXII

Chris – using regex solves item 1 and should be done anyway to avoid whitespace problems in version numbers.

Allan Thomson,
CTO, Lookingglass Cyber Solutions
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From: Chris Larsen <Chris_Larsen@symantec.com>
Date: Thursday, March 1, 2018 at 10:15 AM
To: Allan Thomson <athomson@lookingglasscyber.com>, Mark Davidson <Mark.Davidson@nc4.com>, Bret Jordan <Bret_Jordan@symantec.com>, "cti@lists.oasis-open.org" <cti@lists.oasis-open.org>
Subject: Re: [cti] Advertising a CSD version of STIX and TAXII

Speaking as a coder, there are tigers down both paths:

- If I look for "2.1" (or whatever string) as an exact/specific match, I end up rejecting the suffixed strings, even if I probably could have handled their version.

- If I look for a match that simply *contains* the "2.1", then I accept any of the variants, but then risk having something break internally when the non-compatible bit that I'm not expecting hits my parser.

...

So I end up coding to (my interpretation of) whatever version I'm on, and gracefully rejecting whatever bits of input don't match up with my expectation... (This is what robust input-handling code always tries to do. So it may not matter much.)

That said, I do like the suffix idea, since it has the promise of alerting the input engine very early in the process that there may be incompatibilities (because I don't get the exact match for the "2.1" string), but that I can expect most of the content to work (since I did get a "contains" match).

This is why I've always been a bit jealous of the electronics guys getting to use the word "hardware", because -- darn it! -- software is hard.

--Chris

Chris Larsen

Architect, WebPulse Threat Research Lab

Symantec

From: cti@lists.oasis-open.org <cti@lists.oasis-open.org> on behalf of Allan Thomson <athomson@lookingglasscyber.com>
Sent: Thursday, March 1, 2018 10:37:42 AM
To: Mark Davidson; Bret Jordan; cti@lists.oasis-open.org
Subject: Re: [cti] Advertising a CSD version of STIX and TAXII

Mark – I generally agree with your points.

However, when issues occur in interoperability having the version of 2.1-CSD01 vs 2.1-CSD02 shared between systems will help debug/issues to be resolved.

I don’t see including the longer version information hurts your goals/statements but helps interop/debug.

Regards

Allan

From: Mark Davidson <Mark.Davidson@nc4.com>
Date: Thursday, March 1, 2018 at 9:30 AM
To: Allan Thomson <athomson@lookingglasscyber.com>, Bret Jordan <Bret_Jordan@symantec.com>, "cti@lists.oasis-open.org" <cti@lists.oasis-open.org>
Subject: Re: [cti] Advertising a CSD version of STIX and TAXII

I’m in favor of option #1, as indicated by my comments on the issue, which I’ll reiterate here:

I'm personally in favor of using the plain version string, e.g., version=2.1 for all CSDs, for the following reasons:
1. I don't understand why the stated problem is important to solve - no supporting evidence has been given in this thread, just a problem statement and various proposed solutions.
2. Each new CSD and CS will require code changes to content negotiation, which increases the chances of interoperability breaking. If the change had supporting arguments, then I might view this tradeoff as worthwhile.
3. I don't think the community in general will support multiple CSDs at once, I see the community supporting the latest CSD/CS. For instance, I don't see testing multiple CSDs at a plugfest - I see us doing interop testing for just the most recent CSD or CS.
I guess my biggest concern is - whyis this a problem worth solving? I can see drawbacks for the various solutions proposed, though I'm not able to reason whether or not there are benefits to them.

In terms of what I'd bring to a plugfest or use as a baseline for a vendor integration, I'd only bring something that implements the most recent CSD or CS, and I would not care one bit about compatibility with older CSDs.

I want TAXII 2.1 compatibility issues to arise when two vendors implement different CSDs/CSs, because that's how we'll move the fastest toward interoperable TAXII 2.1 implementations in the marketplace.

Thank you.
-Mark

From: <cti@lists.oasis-open.org> on behalf of Allan Thomson <athomson@lookingglasscyber.com>
Date: Thursday, March 1, 2018 at 12:13 PM
To: Bret Jordan <Bret_Jordan@symantec.com>, "cti@lists.oasis-open.org" <cti@lists.oasis-open.org>
Subject: Re: [cti] Advertising a CSD version of STIX and TAXII

I suggest Option 2) is preferred.

For orgs that don’t care about the sub-version information they can parse the version string for the <major>.<minor> information and ignore the rest.

For orgs that care they can use the full version information.

Allan

From: "cti@lists.oasis-open.org" <cti@lists.oasis-open.org> on behalf of Bret Jordan <Bret_Jordan@symantec.com>
Date: Thursday, March 1, 2018 at 9:06 AM
To: "cti@lists.oasis-open.org" <cti@lists.oasis-open.org>
Subject: [cti] Advertising a CSD version of STIX and TAXII

All,

We have been having a discussion on Slack (#taxii) and in the TAXII Github issue tracker for issue 49 (https://github.com/oasis-tcs/cti-taxii2/issues/49) about how to handle, or if we should handle, the ability to advertise a CSD / draft version that is supported by a solution. As we have not been able to come to consensus, I am asking the broader community for comments and feedback.

Problem:

As we begin to release CSDs for STIX and TAXII 2.1 and the amount of time between releases grows, I believe it will be important for systems to know and understand which version, even a draft version, that the solution currently supports to make sure it can work seamlessly.

Options:

1) Do nothing. Always advertise "2.1". So for CSD01, CSD02, CSD03, etc, you would always just advertise "2.1".

The risks to this that I see are, clients will have no way of knowing if their product is talking to another product that supports that same version of features. If everything was always additive, this "might" be okay. However, given our new process and how concepts can be dropped before the final CS, if they do not have support or code, then a client with support for CSD02 might not work with a client that supports CSD03. And there would be no way for the clients to know that, without two humans talking it through.

Also we may have a situations where something is added to CSD01 and then radically changed in CSD02 due to issues that are found during development. If this happens, a server that is hosting content and is able to update more quickly, will have no way of telling a client (that has not yet updated) that it is using the newer version.

2) Add some sort of designation or suffix to the end of the version that represents an ever increasing value that can easily distinguish the version you are using. Say for CSD01 through CSD03 you could do 2.1-draft01, 2.1-draft02, 2.1-draft03, and then when the final version is ready for a CS level release, the suffix would be dropped and the version would be just 2.1.

Thoughts?

Bret

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