feat(base-cluster/monitoring): set code_challenge_method for oauth2-proxy

[cwrau]

This prevents token interceptions

Summary by CodeRabbit

• Chores
  • Updated monitoring configuration to explicitly set the OAuth2 code challenge method to "S256" for improved OIDC provider compatibility.

[coderabbitai]

Walkthrough

The oauth-proxy HelmRelease configuration within the kube-prometheus-stack was updated to explicitly set the OAuth2 code challenge method to "S256" in the OIDC provider configuration. No other aspects of the deployment or logic were changed.

Changes

File(s)	Change Summary
charts/base-cluster/templates/monitoring/kube-prometheus-stack/oauth-proxy.yaml	Added code_challenge_method = "S256" to OAuth2 config

Suggested labels

base-cluster

Suggested reviewers

• tasches
• marvinWolff

Poem

A line of code, a method set,
"S256"—the safest bet!
Oauth-proxy stands secure and tall,
Guarding clusters, one and all.
With every hop and every byte,
The rabbits dance—security's light!
🐇🔐

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[Copilot]

Pull Request Overview

This PR enforces PKCE by setting the OAuth2 Proxy’s code_challenge_method to "S256", preventing token interception.

• Adds code_challenge_method = "S256" to the OAuth2 Proxy configuration in the Helm chart.
• Enhances security posture by enabling PKCE for all deployments.

Comments suppressed due to low confidence (1)

charts/base-cluster/templates/monitoring/kube-prometheus-stack/oauth-proxy.yaml:68

• Add or update a Helm chart test (e.g., using Chart Testing or a CI job) to assert that code_challenge_method is present and correctly rendered in the generated OAuth Proxy config.

code_challenge_method = "S256"

[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

charts/base-cluster/templates/monitoring/kube-prometheus-stack/oauth-proxy.yaml (1)

68-68: Make PKCE method configurable and verify chart support
Consider exposing code_challenge_method via a Helm value (e.g., global.authentication.oauthProxy.codeChallengeMethod) and templating it with {{ .Values.global.authentication.oauthProxy.codeChallengeMethod | quote }} to allow future overrides. Additionally, verify that the Bitnami oauth2-proxy chart version in use supports the code_challenge_method parameter to avoid compatibility issues.

📜 Review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 372c92b and d1bd78d.

📒 Files selected for processing (1)

• charts/base-cluster/templates/monitoring/kube-prometheus-stack/oauth-proxy.yaml (1 hunks)

⏰ Context from checks skipped due to timeout of 90000ms (3)

• GitHub Check: generateDiffCommentBody
• GitHub Check: lint helm chart (base-cluster)
• GitHub Check: wait-for-checks

🔇 Additional comments (1)

charts/base-cluster/templates/monitoring/kube-prometheus-stack/oauth-proxy.yaml (1)

68-68: Explicit PKCE enforcement added
Explicitly setting code_challenge_method = "S256" enforces a secure PKCE flow, mitigating authorization code interception attacks.

[teutonet-bot]

🤖 I have diffed this beep boop

"/$namespace/$kind/$name.yaml" for normal resources
"/$namespace/HelmRelease/$name/$namespace/$kind/$name.yaml" for HelmReleases <- this is recursive
'null' means it's either cluster-scoped or it's in the default namespace for the HelmRelease

charts/base-cluster/ci/monitoring-ingress-unauthenticated-values.yaml

charts/base-cluster/ci/rbac-values.yaml

charts/base-cluster/ci/pagerduty-values.yaml

charts/base-cluster/ci/velero-backupStorageLocations-gen-values.yaml

charts/base-cluster/ci/flux-gitrepositories-gen-values.yaml

charts/base-cluster/ci/traefik-ingress-values.yaml

charts/base-cluster/ci/imagepullsecrets-values.yaml

charts/base-cluster/values.yaml

charts/base-cluster/ci/artifacthub-values.yaml

charts/base-cluster/ci/disabled-ingress-values.yaml

charts/base-cluster/ci/priorityclasses-values.yaml

[charts/base-cluster/ci/deadmansswitch-values.yaml](

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charts/base-cluster/ci/monitoring-oidc-values.yaml

charts/base-cluster/ci/basic-values.yaml

charts/base-cluster/ci/monitoring-oidc-ingress-disabled-values.yaml

charts/base-cluster/ci/limitrange-resourcequota-values.yaml