Not sure why this is needed, because those file names are already accessible through the derivation value itself, pkgs.mxisd.patches -> [ /home/infinisil/src/nixpkgs/pkgs/servers/mxisd/0001-gradle.patch ]

@infinisil If you have an installed package there is no way to get that. What you suggested is the same as the current situation which is parsing the derivation.

Ah I see. You can still do this though:

$ nix show-derivation $(nix-store -q --deriver \
  /nix/store/681354n3k44r8z90m35hm8945vsp95h1-glibc-2.27) \
  | jq '.[].env.patches'
"/nix/store/r0rc2prwi70hgw4jray5a8sd41fhvjm7-rpcgen-path.patch /nix/store/pp29isd0nvy4jrm9q2f92pjlc83xwa0i-nix-locale-archive.patch /nix/store/5212825a2npxaf7qd81sxfrqq6219rlx-dont-use-system-ld-so-cache.patch /nix/store/mnglr8rr7nl444h7p50ysyq8qd0fm1lm-dont-use-system-ld-so-preload.patch /nix/store/za0pg7fmysrcwrqcal26fnmzw6vycgdn-fix_path_attribute_in_getconf.patch /nix/store/xkd50xxii6k7l1kmw4l5x6xzbhamcs87-allow-kernel-2.6.32.patch /nix/store/nqa9d4yxz1l2cgswzqr1pkm4jfrksm0q-locale-C.diff /nix/store/7kw224hdyxd7115lrqh9a4dv2x8msq2s-fix-x64-abi.patch"

@infinisil the whole point is to not require derivations to be available :)
Your example still makes the assumption that you can pull the glibc derivation which is not always possible as I mentioned in the PR description

Oh right, I forgot that .drv's aren't always present.

So the main use case for this is for end users being able to check what patches their installed software has?

@infinisil yeah. For me the idea is to use Vulnix to automate vulnerability scans of live systems.
I want to be able to do vulnix -S --json on a machine that is deployed from nixops and substituting most of the packages.

I'm 👍 on this idea then :)

Changed from draft to ready to review to get automatic reviewers.
Would be good to get @ckauhaus's opinion still as the Vulnix maintainer.

I haven't been following the discussion on pure evaluation but my gut feeling tells me that the idea of adding structured metadata to the output is a good idea. This is also something that the Python community in their packaging has been banging their heads on and they're moving towards structured, static metadata attached to package releases instead of having to evaluate (untrusted) Python code in some location. Obviously Nix is in a better spot here, but still, my intuition tells me that this might become an ever-repeating corner case issue so I'd be in favor of computing static metadata and attaching that to the output.

The format ($out/nix-support) might need to be thought of a little bit more: Who manages that namespace? Should we use multiple files or a single file? Is the intended consumer better served using a structured format like JSON?

We might want to start with something like what we have now and then deprecate or evolve the format later (adding a version identifier early on could be helpful for consumers).

One specific note on this patch: AFAICT this only includes the metadata on the dev output, but IMHO those should be present in all outputs.

Nix already has a way to keep the structured metadata: keep-derivations = true.
Because patches .drv are referred in derivations they will be present there as well and so this issue is covered there.

Right, however, I'm not sure whether that helps - you can create stores that will never have the derivations in the first place and thus it's not an issue of preventing GC but getting them in the first place ... or did I get that wrong?

True, you can do that. Maybe Nix could have an option require-derivations, although I can imagine that to give trouble as well.

As soon as we have structured attributes, the stdenv could have an output "drv" into which we would copy the .attrs.json.

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Can we revisit this? cc @nikstur (discussions on SBOM at sprint)

@RaitoBezarius Yeah SBOMs would be the right way to go forward with this, I don't know if they were a thing in 2019 when I initially created the issue :D but it certainly is what I wanted to have. SBOM+VEX is probably the thing we need for nix packages, it can be also an artifact that is part of the store path output ?

Sounds like CycloneDX would be the ideal fit. It is an easy to read JSON and can be BOTH a SBOM and a VEX (and many more things) at the same time. We could either expose the SBOM as a passthru argument/derivation or include it in the output of the derivation. You can then use a tool like bombon (which I have written) to collect the SBOMs of the dependencies and assemble them into a single document for an arbitrary closure.

I don't really get the point of this.

If you have an output path on a system but not the accompanying derivation, you're likely managing that system remotely and in that case you have the nix expressions handy.

If you have the need to audit your systems, you should use the Nix expressions directly. The state of a system should always be a direct result of the Nix expressions, so looking at it should contain no more information than was available before which means there's no point looking at it other than to verify it's indeed the result of some Nix expressions.

This is assuming a very Nix expression driven world, but Nix store is a lower level primitive that can be used in more contexts than simply Nix expressions IMHO.

Moreover, not all tooling is going to understand how to derive this information from Nix expressions, having them as part of derivations is a neat way to make them understandable for "simple tooling" (scanners, compliance, etc.).

Then also the patches are put into the dev output which you'll likely not actually have in a system closure as that's part of the build-time closure at best.

Next problem is a minor one but it's still smelly: The patches are now referenced by the dev output which means they become part of its closure. Build-time deps leaking into the output paths doesn't feel right.

Maybe, let's not have patches but SBOMs? Would that solve the smell?

This is assuming a very Nix expression driven world, but Nix store is a lower level primitive that can be used in more contexts than simply Nix expressions IMHO.

I can't imagine how you'd arrive at output paths in any other way than Nix expressions outside of highly experimental tooling. (well, other than using GUIX); not something you'd do in a productive environment that cares about security enough to warrant checks.

not all tooling is going to understand how to derive this information from Nix expressions

If you care about security at all, you should teach the tooling how to get the info from Nix expressions or use better tooling.

having them as part of derivations is a neat way to make them understandable for "simple tooling" (scanners, compliance, etc.).

Good point.

I'm not against optional support for this sort of thing. If you are forced to use bad tooling for security audits etc., there's no other way. I'd be fine with an opt-in flag to store patches, SBOM or whatever lesser source information in the output.

Not on my machine though please. I don't need thousands of useless patches in my closure.

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/tweag-nix-dev-update-46/26872/4