OpenCost Security Policy

The OpenCost project greatly appreciates the need for security and timely updates, given our proximity to cloud billing. We are very grateful to the users, security researchers, and developers for reporting security vulnerabilities to us. All reported security vulnerabilities will be carefully assessed, addressed, and responded to.

Code Security

Application code is version controlled using GitHub. All code changes are tracked with full revision history and are attributable to a specific individual. Code must be reviewed and accepted by a different engineer than the author of the change.

Dependabot

OpenCost has Dependabot enabled for assessing dependencies in the project.

Image Signing and Verification

OpenCost container images published from this repository by the tag-triggered release workflow and the develop branch publishing workflow are signed with Sigstore cosign using keyless signatures. Signing is driven by GitHub Actions OIDC — there are no long-lived signing keys to manage or rotate. Each signature is recorded in the public Rekor transparency log, and every signed image is additionally accompanied by a SLSA v1 build provenance attestation produced with cosign attest.

Note: workflow_dispatch runs of build-and-publish-release.yml intentionally skip signing. A manual dispatch runs from a branch ref rather than a tag, so the Fulcio certificate identity would not match the refs/tags/vX.Y.Z pattern that verification tooling and the Kyverno policy below pin to — a signature produced under a branch identity would be silently rejected by those admission policies anyway. To produce a verifiable release, push a vX.Y.Z tag and let the tag event trigger the workflow.

What is signed

Artifact	Registry	Signed by workflow
Release images (`:latest`, `:X.Y.Z`, `:<shorthash>`)	`ghcr.io/opencost/opencost`	`.github/workflows/build-and-publish-release.yml`
Develop images (`:develop-latest`, `:develop-<shorthash>`)	`ghcr.io/opencost/opencost`	`.github/workflows/build-and-publish-develop.yml`
Helm chart OCI artifacts	`ghcr.io/opencost/opencost-helm-chart`	`opencost/opencost-helm-chart` — `.github/workflows/publish.yml`

Signatures are attached to the image by digest, so any tag that resolves to a signed manifest is verifiable regardless of tag mutation.

Expected signing identity

Field	Value
`--certificate-oidc-issuer`	`https://token.actions.githubusercontent.com`
`--certificate-identity` (release tag `vX.Y.Z`)	`https://github.com/opencost/opencost/.github/workflows/build-and-publish-release.yml@refs/tags/vX.Y.Z`
`--certificate-identity-regexp` (any release)	`^https://github\.com/opencost/opencost/\.github/workflows/build-and-publish-release\.yml@refs/tags/v[0-9]+\.[0-9]+\.[0-9]+$`
`--certificate-identity-regexp` (develop)	`^https://github\.com/opencost/opencost/\.github/workflows/build-and-publish-develop\.yml@refs/heads/develop$`

Verifying an image signature

Install cosign (go install github.com/sigstore/cosign/v2/cmd/cosign@latest or see the install guide), then verify a specific release:

VERSION=1.115.0 # replace with the release you are verifying

cosign verify \
  --certificate-identity "https://github.com/opencost/opencost/.github/workflows/build-and-publish-release.yml@refs/tags/v${VERSION}" \
  --certificate-oidc-issuer "https://token.actions.githubusercontent.com" \
  "ghcr.io/opencost/opencost:${VERSION}"

A successful verification prints the signed payload and confirms the Rekor inclusion proof.

Verifying SLSA provenance

Each image also has a SLSA v1 provenance attestation. Inspect it with:

VERSION=1.115.0 # replace with the release you are verifying

cosign verify-attestation \
  --type slsaprovenance1 \
  --certificate-identity-regexp "^https://github\.com/opencost/opencost/\.github/workflows/build-and-publish-release\.yml@refs/tags/v[0-9]+\.[0-9]+\.[0-9]+$" \
  --certificate-oidc-issuer "https://token.actions.githubusercontent.com" \
  "ghcr.io/opencost/opencost:${VERSION}"

Verifying the Helm chart signature

Helm chart OCI artifacts published by opencost/opencost-helm-chart are signed by the same keyless pattern. Verify a pulled chart with:

CHART_VERSION=1.45.0 # replace with the chart version you are verifying

cosign verify \
  --certificate-identity-regexp "^https://github\.com/opencost/opencost-helm-chart/\.github/workflows/publish\.yml@refs/tags/v[0-9]+\.[0-9]+\.[0-9]+$" \
  --certificate-oidc-issuer "https://token.actions.githubusercontent.com" \
  "ghcr.io/opencost/opencost-helm-chart/opencost:${CHART_VERSION}"

Admission-time enforcement

The following Kyverno ClusterPolicy blocks any pod whose image is pulled from ghcr.io/opencost/opencost unless it carries a valid keyless signature from the release workflow. An equivalent pattern works with Sigstore policy-controller and Connaisseur.

apiVersion: kyverno.io/v2beta1
kind: ClusterPolicy
metadata:
  name: verify-opencost-image-signatures
spec:
  validationFailureAction: Enforce
  background: false
  webhookTimeoutSeconds: 30
  rules:
    - name: verify-opencost-signed-by-release-workflow
      match:
        any:
          - resources:
              kinds:
                - Pod
      verifyImages:
        - imageReferences:
            - "ghcr.io/opencost/opencost:*"
          attestors:
            - entries:
                - keyless:
                    subjectRegExp: "^https://github\\.com/opencost/opencost/\\.github/workflows/build-and-publish-release\\.yml@refs/tags/v[0-9]+\\.[0-9]+\\.[0-9]+$"
                    issuer: "https://token.actions.githubusercontent.com"
                    rekor:
                      url: "https://rekor.sigstore.dev"

If your cluster pulls development builds, extend imageReferences with ghcr.io/opencost/opencost:develop-* and add a second attestor entry whose subjectRegExp targets the build-and-publish-develop.yml workflow.

Supported Versions

OpenCost provides security updates for the two most recent minor versions released on GitHub.

For example, if v1.102.0 is the most recent stable version, we will address security updates for v1.101.0 and later. Once v1.103.0 is released, we will no longer provide updates for v1.101.x releases.

Reporting a Vulnerability

The OpenCost project has enabled Private vulnerability reporting for our repositories which allows for direct reporting of issues to administrators and maintainers in a secure fashion. Please include a thorough description of the issue, the steps you took to create the issue, affected versions, and, if known, mitigations for the issue. The team will help diagnose the severity of the issue and determine how to address the issue. Issues deemed to be non-critical will be filed as GitHub issues. Critical issues will receive immediate attention and be fixed as quickly as possible.

Disclosure policy

For known public security vulnerabilities, we will disclose the disclosure as soon as possible after receiving the report. Vulnerabilities discovered for the first time will be disclosed in accordance with the following process:

The received security vulnerability report shall be handed over to the security team for follow-up coordination and repair work.
After the vulnerability is confirmed, we will create a draft Security Advisory on GitHub that lists the details of the vulnerability.
Invite related personnel to discuss the fix.
Fork the temporary private repository on GitHub, and collaborate to fix the vulnerability.
After the fixed code is merged into all supported versions, the vulnerability will be publicly posted in the GitHub Advisory Database.

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