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Enforce structural rules in CRD OpenAPIv3 schema validation #131836

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Enforce structural rules in CRD OpenAPIv3 schema validation #131836

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tomoish
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@tomoish tomoish commented May 18, 2025 •
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What type of PR is this?

/kind bug

What this PR does / why we need it:

Tightens CRD OpenAPI v3 validation. A schema that sets items,
properties, or additionalProperties is now accepted only when
the owning schema declares the matching type:

  • items : parent type must be "array"
  • properties: parent type must be "object"
  • additionalProperties: parent type must be "object"

These checks keep CRDs structurally valid, prevent runtime panics, and
align the apiserver with OpenAPI v3 constraints.

Key changes

  • Add logic to ValidateCustomResourceDefinitionOpenAPISchema
  • Extend unit tests to cover the new conditions
  • Remove redundant expectations in existing tests

Which issue(s) this PR fixes:

Fixes #126273

Special notes for your reviewer:

Does this PR introduce a user-facing change?

CRD OpenAPI v3 validation now rejects schemas that set `items` when the parent type is not `"array"`, or `properties` / `additionalProperties` when the parent type is not `"object"`.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

@tomoish
Enforce structural rules in CRD OpenAPIv3 schema validation
6671000 
Add strict checks so that a schema containing `items`, `properties`, or
`additionalProperties` is only accepted when the parent `type` is
`array` or `object` as required:

* `items` allowed only when `type: array`
* `properties` allowed only when `type: object`
* `additionalProperties` allowed only when `type: object`

These rules prevent non-structural schemas from being stored in Custom
Resource Definitions and avoid runtime panics or inconsistent behavior.
@k8s-ci-robot k8s-ci-robot added release-note Denotes a PR that will be considered when it comes time to generate release notes. size/L Denotes a PR that changes 100-499 lines, ignoring generated files. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. do-not-merge/needs-kind Indicates a PR lacks a `kind/foo` label and requires one. do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. labels May 18, 2025
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Hi @tomoish. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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@k8s-ci-robot k8s-ci-robot added needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. needs-priority Indicates a PR lacks a `priority/foo` label and requires one. kind/api-change Categorizes issue or PR as related to adding, removing, or otherwise changing an API and removed do-not-merge/needs-kind Indicates a PR lacks a `kind/foo` label and requires one. labels May 18, 2025
@k8s-ci-robot k8s-ci-robot requested review from cici37 and yujuhong May 18, 2025 13:23
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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: tomoish
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tomoish commented May 18, 2025

/sig api-machinery
/kind bug

@k8s-ci-robot k8s-ci-robot added sig/api-machinery Categorizes an issue or PR as relevant to SIG API Machinery. kind/bug Categorizes issue or PR as related to a bug. and removed do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. labels May 18, 2025
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This PR may require API review.

If so, when the changes are ready, complete the pre-review checklist and request an API review.

Status of requested reviews is tracked in the API Review project.

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/cc @jpbetz @sttts
/triage accepted

@k8s-ci-robot k8s-ci-robot requested review from jpbetz and sttts May 20, 2025 20:15
@k8s-ci-robot k8s-ci-robot added triage/accepted Indicates an issue or PR is ready to be actively worked on. and removed needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. labels May 20, 2025
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jpbetz commented May 20, 2025 •
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While I would love to clean this up. I'm hesitant because it could break in-use CRDs. Having both "items" and "properties" is allowed today and so it's possible to have CRDs that work fine. While the schemas for such a CRD are clearly a mess, and as much as I'd like to make that better, I don't really want to cause production issues by making such CRDs invalid.

I support modifying validation to return warnings in these cases.

@JoelSpeed @yongruilin - Could we also lint CRDs for this?

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This is definitely something we should be linting, making sure that all markers are applied to the correct object vs array vs other (int/string etc)

I'll create an issue

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jpbetz commented May 21, 2025

@liggitt suggested we also check what we publish to /openapi for cases like this. If the CRD schema has type=object with both items and properties set, we should not show the items in published openapi.

This sounds like a great idea to me.

@k8s-ci-robot k8s-ci-robot added the needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. label Jun 26, 2025
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PR needs rebase.

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@cici37 cici37 Awaiting requested review from cici37

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Adding additional guards on CRD schema
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