Singularity Image Format (SIF) support

[tri-adam]

What would you like to be added:

Support for generating an SBOMs from containers packaged in the Singularity Image Format (SIF) :

syft packages sif:image.sif

Why is this needed:

Singularity users package their containers in SIF, and are increasingly interested in supply chain security. It'd be nice if they could use syft to generate SBOMs.

Additional context:

Sylabs has done some initial research on integrating SIF and Syft, and we'd be happy to open pull request(s) with that initial work if there's support for this feature being added to syft.

Related: sylabs/sif#190

[luhring]

Sounds great! We'd love to help guide any PRs to the finish line here. Let us know what you need from us.

[tri-adam]

Awesome!

I think the main question was around where to add functionality between syft and stereoscope repos. @Poluect, could you PR your code as a starting point to get the discussion started?