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Subject: Re: [cti] CybOX Object Extensions
I’ve just added some quasi-normative text around this concept in the CybOX 3.0 pre-draft spec [1] - I look forward to any comments or feedback. As far extension names, I agree that they don’t need to be extremely verbose, and given that they’re applicable
only to a particular object, I don’t think we need to include the name of their corresponding object. Therefore, I would suggest we go with simple names that provide the minimum detail necessary to identify the extension, such as ‘metadata’, ‘ext3’, ‘pebinary’,
etc.
[1] https://docs.google.com/document/d/1DdS-NrVTjGJ3wvCJ7dbSlhYeiaWS6G6dOXu2F3POpUs/edit?usp=sharing
Regards,
Ivan
From: Mark Davidson <mdavidson@soltra.com>
Date: Thursday, February 11, 2016 at 5:47 AM To: Ivan Kirillov <ikirillov@mitre.org>, "cti@lists.oasis-open.org" <cti@lists.oasis-open.org> Subject: Re: [cti] CybOX Object Extensions Ivan,
I generally like where this is going. Could you write down what you would consider the current line of thought in the CybOX pre-draft spec? Capturing your bullet points and example in the document would help me understand them better in context. It will
also help us make progress toward our MVP.
I think having overlapping properties is probably OK. For instance, would I rather parse a single EXT2/3 extension than an EXT2 extension and an EXTGeneric extension, even if that meant EXT2/EXT3 had duplicate structures. If the necessary properties for
a given thing are spread across multiple extensions that makes it harder to parse IMO.
From my perspective (and I’m curious what others think) I think you are on the right track overall and I’d be interested in seeing more of these thoughts captured in the pre-draft spec even if we don’t talk about it on the list fist. Personally I’d love
to be able to come back and say “I think Section XYZ is pretty much right with a couple nits; I think Section ABC is entirely wrong and should be deleted”.
Thank you.
-Mark
P.S. Minor nit – would the file object have a type field?
P.P.S. Minot nit #2 – I think I might prefer slightly different names for the extensions (e.g., `file.metadata`), but that’s not core to the topic.
From: <cti@lists.oasis-open.org> on behalf of "Kirillov, Ivan A." <ikirillov@mitre.org>
Date: Wednesday, February 10, 2016 at 1:00 PM To: "cti@lists.oasis-open.org" <cti@lists.oasis-open.org> Subject: [cti] CybOX Object Extensions Sending this to the broader CTI list since it’s part of the STIX/CybOX Indicator tranche.
I don’t believe we have consensus yet on the concept of CybOX extensions, so here’s our current thinking to help summarize where we stand:
Here’s a JSON example of what extensions on a File Object would look like:
{ "hashes": [{ "type": "md5", "hash-value": "3773a88f65a5e780c8dff9cdc3a056f3" }], "size": 25537, "extended-properties": { "FileMetadataExtension": {"mime-type": "vnd.microsoft.portable-executable"}, "EXT3FileExtension": {"inode": "34483923"}, "PEBinaryFileExtension": {"exports": [{"name": "foo_app"}]} } } Besides some logistical questions around extension management and versioning [2], the biggest open question is around extension design, especially whether we should permit overlapping properties. Our current thinking is that extensions are defined independently
and cannot extend/sub-class each other (to avoid the same issues that we’ve had with this approach). What this means in practice is that there could be cases where two extensions share one or more properties; for example, if we have an EXT2FileExtension and
EXT3FileExtension, both could have the “inode” property. To get around this, we could create a “generic” EXTFileExtension that has a set of properties common to all EXT file systems, and have the EXT2FileExtension and EXT3FileExtension contain only their unique
set of properties.
Are there any thoughts on how we should approach this? Should we permit overlapping properties in extensions?
Regards,
Ivan
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