fix(golib-release): verify cosign signature against reusable workflow identity#165
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… identity Keyless signing performed inside a reusable workflow produces a certificate whose SAN identity is the reusable workflow's job_workflow_ref (e.g. .../golib-create-release.yml@refs/heads/main), not the calling repository. The verify step matched https://github.com/<caller>/* and failed: failed to verify certificate identity: no matching CertificateIdentity found ... got "https://github.com/netresearch/.github/.github/workflows/ golib-create-release.yml@refs/heads/main" Match the reusable workflow's own identity instead. Observed on netresearch/go-cron v0.15.0 — the first release to actually run cosign signing (earlier the caller lacked id-token/attestations permissions). Signed-off-by: Sebastian Mendel <github@sebastianmendel.de>
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Pull request overview
This PR fixes cosign signature verification in the golib-create-release reusable workflow by validating against the reusable workflow’s own OIDC certificate identity (as produced by keyless signing inside a reusable workflow), instead of the calling repository identity.
Changes:
- Update
cosign verify-blobto use the reusable workflow identity pattern rather than${{ github.repository }}. - Add inline documentation explaining why the reusable workflow identity must be used for verification.
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| cosign verify-blob \ | ||
| --bundle checksums.txt.sigstore.json \ | ||
| --certificate-identity-regexp "https://github.com/${REPO}/*" \ | ||
| --certificate-identity-regexp "^https://github\.com/netresearch/\.github/\.github/workflows/golib-create-release\.yml@" \ | ||
| --certificate-oidc-issuer "https://token.actions.githubusercontent.com" \ |
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Problem
The
golib-create-releasereusable workflow's Verify Cosign signature step uses--certificate-identity-regexp "https://github.com/${github.repository}/*"(the calling repo). But keyless signing performed inside a reusable workflow yields a certificate whose SAN identity is the reusable workflow'sjob_workflow_ref, not the caller. So verification fails:Observed on netresearch/go-cron v0.15.0 — the first release to actually run cosign signing (prior releases couldn't even start the workflow until the caller perms were fixed in #163).
Fix
Verify against this workflow's own identity:
Follow-up (not in this PR)
Downstream verification instructions in consuming repos' release notes should likewise reference the reusable-workflow identity rather than the per-repo identity.