fix(security): restrict tenant gateway hostnames - #2740
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devantler
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Aug 9, 2026
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Static exact-head review of db37ba3d5b047a86044c3a43d8ff605137e0c66e; the branch was not checked out or executed. The inline P1 is blocking.
Additive-list conflict in the cluster-policies kustomization: this branch adds `restrict-wedding-app-route-hostnames.yaml`, main added `restrict-tenant-issuer-refs.yaml`. Both belong, kept in the list's existing alphabetical order. The merge also drops `verify-ksail-images.yaml`, which main deleted in 41336ed (#2836) — the file no longer exists in main's tree, so keeping the reference would break the build. Verified by diffing the resolved resource list against both parents: nothing of main's dropped, nothing beyond the union added, every referenced file present, list still sorted. Both overlays validate (565 files each), with both newly unioned policies explicitly covered.
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DIRTY → mergeable: conflict with The conflict in The merge also drops Verified rather than assumed — a marker/count check is structurally blind to a re-parented entry, so
One unresolved review thread remains on this PR, which I have not touched. |
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The policy matched only the wedding-app namespace, but three namespaces bind the tenant-edit ClusterRole and reconcile tenant-controlled manifests as their own impersonated ServiceAccount: wedding-app, ascoachingogvaner and doggy-countdown. The other two could therefore set any hostname on the shared wildcard Gateway, including each other's, and a hostname-less route matches every hostname on the listener. Generalise it to restrict-tenant-route-hostnames, with a per-tenant allow-list rule for each of the three (their hostnames are not derivable from the namespace name) and a catch-all that denies HTTPRoutes in any other ksail tenant namespace, so onboarding a tenant without declaring its hostnames fails loudly instead of inheriting the wildcard. Each rule keeps the flux-system kustomize-controller carve-out used by the sibling tenant policies, so platform-applied routes are unaffected; that makes the policy admission-only, as it is for those siblings. Add kyverno fixtures, which the old policy had none of, covering each tenant's approved set, the cross-tenant claim, hostname-less and mixed routes, the fail-closed catch-all, and a controlled pair proving the platform carve-out is what admits an otherwise-denied platform route.
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Valid — fixed in The policy is now Two things I deliberately did not do:
Verification. New I also checked the fixtures are not vacuous. Weakening the Worth flagging that a stronger ablation did not fire: deleting a rule outright leaves the suite Both overlays validate (565 files each, |
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Named blocker: What actually failsThe job's headline output is a wall of
Evidence it is not this PR's doing
So this is a standing tax on every manifest PR, not a defect in the tenant-hostname work. The fixRe-approve the constant, following the convention #2866 established for exactly this — its diff
For this PR the expected membership delta is: Why I did not apply it hereTwo reasons, both worth stating rather than working around:
State of this PR otherwiseThe [P1] is fixed and resolved, both overlays validate (565 files each, local and prod), naming I also filed #3152 separately: the Already tracked: #2768 — "The EKS authorization surface hash goes stale on every HelmRelease |
…face Removing the built-in aggregate-to-edit label from gateway-tenant-edit and adding the restrict-tenant-route-hostnames admission policy move the aggregate authorization surface fingerprint. Approve the new value with the measured base-vs-head delta, per the convention in this file. The delta is a privilege reduction plus one Enforce admission guardrail: no identity, binding, ServiceAccount or verb is added, and the validator reported no per-resource mismatch.
Code Coverage OverviewLanguages: Go Go / code-coverage/goThe overall coverage in commit f7d8243 in the Show a code coverage summary of the most covered files.
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@coderabbitai review |
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🧠 Learnings used✅ Action performedReview finished.
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Unblocked: required checks were failing, now CLEAN (33/33 green). The failure was the authorization-surface gate in 1. The 30+ 2. The fingerprint the failing run printed was already stale. That run was created What the approval covers, measured base
Nothing reaching the Related: #2866 overlaps this PR and is superseded by it — details in a comment there. Its Remaining gate: one green review at |
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📝 WalkthroughWalkthroughAdds an enforced, admission-only Kyverno Possibly related PRs
🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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Actionable comments posted: 1
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Inline comments:
In
`@k8s/bases/infrastructure/cluster-policies/best-practices/restrict-tenant-route-hostnames.yaml`:
- Line 61: Remove the deprecated spec.validationFailureAction setting and add
validate.failureAction: Enforce to each of the four validation rules, preserving
enforcement for every HTTPRoute hostname policy.
ℹ️ Review info
⚙️ Run configuration
Configuration used: Repository YAML (base), Organization UI (inherited)
Review profile: ASSERTIVE
Plan: Pro Plus
Run ID: 8899968e-f4b3-4042-9b56-d7b19a3bebb8
📒 Files selected for processing (12)
k8s/bases/infrastructure/cluster-policies/best-practices/restrict-tenant-route-hostnames.yamlk8s/bases/infrastructure/cluster-policies/kustomization.yamlk8s/bases/infrastructure/cluster-roles/gateway-tenant-edit.yamlscripts/validate-eks-ci-role-policy/main.gotests/restrict-tenant-route-hostnames/kyverno-test.yamltests/restrict-tenant-route-hostnames/platform-author/kyverno-test.yamltests/restrict-tenant-route-hostnames/platform-author/resources.yamltests/restrict-tenant-route-hostnames/platform-author/user-info.yamltests/restrict-tenant-route-hostnames/platform-author/values.yamltests/restrict-tenant-route-hostnames/resources.yamltests/restrict-tenant-route-hostnames/user-info.yamltests/restrict-tenant-route-hostnames/values.yaml
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📓 Path-based instructions (1)
**/*.{yaml,yml}
📄 CodeRabbit inference engine (AGENTS.md)
**/*.{yaml,yml}: Never run a cluster
Put a change in the layer that matches its scope
Files:
tests/restrict-tenant-route-hostnames/platform-author/values.yamltests/restrict-tenant-route-hostnames/platform-author/user-info.yamltests/restrict-tenant-route-hostnames/user-info.yamltests/restrict-tenant-route-hostnames/values.yamlk8s/bases/infrastructure/cluster-policies/kustomization.yamltests/restrict-tenant-route-hostnames/platform-author/resources.yamltests/restrict-tenant-route-hostnames/platform-author/kyverno-test.yamltests/restrict-tenant-route-hostnames/resources.yamlk8s/bases/infrastructure/cluster-roles/gateway-tenant-edit.yamltests/restrict-tenant-route-hostnames/kyverno-test.yamlk8s/bases/infrastructure/cluster-policies/best-practices/restrict-tenant-route-hostnames.yaml
🧠 Learnings (6)
📚 Learning: 2026-08-11T12:41:28.242Z
Learnt from: devantler
Repo: devantler-tech/platform PR: 3082
File: k8s/bases/infrastructure/controllers/coroot/cron-job-cnpg-degraded-alert.yaml:113-120
Timestamp: 2026-08-11T12:41:28.242Z
Learning: When changing behavior in Kubernetes manifests or related documentation, review comments and documentation in YAML/YML and Markdown files for statements describing the previous behavior. Update every stale statement in the same change so the repository’s explanatory text remains consistent with the implementation.
Applied to files:
tests/restrict-tenant-route-hostnames/platform-author/values.yamltests/restrict-tenant-route-hostnames/platform-author/user-info.yamltests/restrict-tenant-route-hostnames/user-info.yamltests/restrict-tenant-route-hostnames/values.yamlk8s/bases/infrastructure/cluster-policies/kustomization.yamltests/restrict-tenant-route-hostnames/platform-author/resources.yamltests/restrict-tenant-route-hostnames/platform-author/kyverno-test.yamltests/restrict-tenant-route-hostnames/resources.yamlk8s/bases/infrastructure/cluster-roles/gateway-tenant-edit.yamltests/restrict-tenant-route-hostnames/kyverno-test.yamlk8s/bases/infrastructure/cluster-policies/best-practices/restrict-tenant-route-hostnames.yaml
📚 Learning: 2026-07-01T21:13:36.950Z
Learnt from: devantler
Repo: devantler-tech/platform PR: 2359
File: k8s/bases/apps/actual-budget/helm-release.yaml:62-111
Timestamp: 2026-07-01T21:13:36.950Z
Learning: When reviewing Kustomize/Helm YAML in this repo, keep the base vs provider overlay split: `k8s/bases/apps/**` and `k8s/bases/infrastructure/**` should contain each app’s full, environment-agnostic configuration (including base-level postRenderer Kustomize patches such as deployment strategy, topology spread, probes, and env injection). `k8s/providers/{docker,hetzner}/**` should only add small provider-specific deltas (e.g., `interval`, `persistence.size`) via patch files (like `k8s/providers/<provider>/apps/<app>/patches/helm-release-patch.yaml`). If configuration is identical across providers (e.g., OIDC/OAuth env vars where `${domain}` is resolved per cluster via envsubst), it belongs in the base and must not be duplicated into provider overlays.
Applied to files:
k8s/bases/infrastructure/cluster-policies/kustomization.yamlk8s/bases/infrastructure/cluster-roles/gateway-tenant-edit.yamlk8s/bases/infrastructure/cluster-policies/best-practices/restrict-tenant-route-hostnames.yaml
📚 Learning: 2026-08-08T15:10:00.349Z
Learnt from: devantler
Repo: devantler-tech/platform PR: 3017
File: k8s/bases/infrastructure/coroot/components/crossplane-sync-exporter/deployment.yaml:13-21
Timestamp: 2026-08-08T15:10:00.349Z
Learning: In the devantler-tech/platform repository, Checkov CI scans source manifests with `--skip-framework kustomize` rather than rendered Kustomize overlays. To suppress a Checkov finding on a base manifest, place the appropriate `checkov.io/skip*` annotation directly in that base YAML file; an overlay patch will not suppress findings reported for the source file.
Applied to files:
k8s/bases/infrastructure/cluster-policies/kustomization.yamlk8s/bases/infrastructure/cluster-roles/gateway-tenant-edit.yamlk8s/bases/infrastructure/cluster-policies/best-practices/restrict-tenant-route-hostnames.yaml
📚 Learning: 2026-08-08T15:10:00.350Z
Learnt from: devantler
Repo: devantler-tech/platform PR: 3017
File: k8s/bases/infrastructure/coroot/components/crossplane-sync-exporter/deployment.yaml:13-21
Timestamp: 2026-08-08T15:10:00.350Z
Learning: For Kubernetes manifests under k8s/bases/, keep workload-related Checkov exception annotations (checkov.io/skip*) in the base manifest when the checked condition is defined there and CI scans that source manifest directly. Do not move these annotations to overlays solely because the base is immutable; keeping them with the workload ensures the disposition applies consistently to every consumer of the base.
Applied to files:
k8s/bases/infrastructure/cluster-policies/kustomization.yamlk8s/bases/infrastructure/cluster-roles/gateway-tenant-edit.yamlk8s/bases/infrastructure/cluster-policies/best-practices/restrict-tenant-route-hostnames.yaml
📚 Learning: 2026-08-08T21:23:32.529Z
Learnt from: devantler
Repo: devantler-tech/platform PR: 3025
File: k8s/bases/infrastructure/controllers/kubescape/helm-release.yaml:97-133
Timestamp: 2026-08-08T21:23:32.529Z
Learning: In the devantler-tech/platform repository, modify Kubernetes manifests directly under k8s/bases/ when a configuration change should apply to all Kustomize overlays. Use provider- or cluster-specific overlay patches only for changes that are intentionally limited to those overlays.
Applied to files:
k8s/bases/infrastructure/cluster-policies/kustomization.yamlk8s/bases/infrastructure/cluster-roles/gateway-tenant-edit.yamlk8s/bases/infrastructure/cluster-policies/best-practices/restrict-tenant-route-hostnames.yaml
📚 Learning: 2026-08-15T07:39:50.444Z
Learnt from: devantler
Repo: devantler-tech/platform PR: 2718
File: k8s/bases/infrastructure/cluster-policies/best-practices/restrict-github-team-management.yaml:19-28
Timestamp: 2026-08-15T07:39:50.444Z
Learning: For all Kyverno ClusterPolicy manifests under k8s/bases/infrastructure/cluster-policies/best-practices/, do not use the deprecated top-level spec.validationFailureAction. Migrate each policy's validation rules to set validate.failureAction per rule, completing the migration for all nine policies with or before the next Kyverno version bump. Track the work under GitHub issue `#3149`.
Applied to files:
k8s/bases/infrastructure/cluster-policies/best-practices/restrict-tenant-route-hostnames.yaml
🔇 Additional comments (12)
k8s/bases/infrastructure/cluster-roles/gateway-tenant-edit.yaml (1)
1-10: LGTM!scripts/validate-eks-ci-role-policy/main.go (1)
436-470: LGTM!k8s/bases/infrastructure/cluster-policies/best-practices/restrict-tenant-route-hostnames.yaml (1)
1-60: LGTM!Also applies to: 62-193
k8s/bases/infrastructure/cluster-policies/kustomization.yaml (1)
16-16: LGTM!tests/restrict-tenant-route-hostnames/kyverno-test.yaml (1)
1-82: LGTM!tests/restrict-tenant-route-hostnames/resources.yaml (1)
1-181: LGTM!tests/restrict-tenant-route-hostnames/values.yaml (1)
1-23: LGTM!tests/restrict-tenant-route-hostnames/user-info.yaml (1)
1-13: LGTM!tests/restrict-tenant-route-hostnames/platform-author/kyverno-test.yaml (1)
1-22: LGTM!tests/restrict-tenant-route-hostnames/platform-author/resources.yaml (1)
1-17: LGTM!tests/restrict-tenant-route-hostnames/platform-author/user-info.yaml (1)
1-12: LGTM!tests/restrict-tenant-route-hostnames/platform-author/values.yaml (1)
1-10: LGTM!
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August 16, 2026 04:01
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Motivation
Every tenant publishes through the same shared platform Gateway, whose listener carries a wildcard certificate — and Gateway API resolves route hostnames with no permission check of its own. A tenant could therefore claim any hostname under that wildcard, including another tenant's, and quietly serve or intercept its traffic. Leaving hostnames off entirely is the strongest form of the same problem: such a route matches every hostname on the listener.
What changed
Two things, both narrowing:
editrole. Thegateway-tenant-editClusterRole drops itsaggregate-to-editlabel, so ordinaryeditbindings in every namespace stop inheriting Gateway API route permissions. Tenants keep exactly the access they already had throughtenant-edit.Verification
Checked against the live production cluster: all four route-carrying tenant namespaces pass unchanged, and no existing route is denied. The policy's test fixtures cover the escalations it exists to stop — claiming another tenant's hostname, smuggling an extra hostname alongside an approved one, and omitting hostnames — plus the platform-applied carve-out.
Note for reviewers
This also updates the approved authorization-surface fingerprint, which is what the change to
scripts/validate-eks-ci-role-policyis for. The reasoning, and the measured before/after, are recorded in a comment below and in the code comment itself.Follow-up filed as #3163 (migrating all policies off a deprecated Kyverno field — unrelated to this change's correctness).