BIT-cosign-2022-36056

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BIT-cosign-2022-36056

Summary: Vulnerabilities with blob verification in sigstore cosign

Details: Cosign is a project under the sigstore organization which aims to make signatures invisible infrastructure. In versions prior to 1.12.0 a number of vulnerabilities have been found in cosign verify-blob, where Cosign would successfully verify an artifact when verification should have failed. First a cosign bundle can be crafted to successfully verify a blob even if the embedded rekorBundle does not reference the given signature. Second, when providing identity flags, the email and issuer of a certificate is not checked when verifying a Rekor bundle, and the GitHub Actions identity is never checked. Third, providing an invalid Rekor bundle without the experimental flag results in a successful verification. And fourth an invalid transparency log entry will result in immediate success for verification. Details and examples of these issues can be seen in the GHSA-8gw7-4j42-w388 advisory linked. Users are advised to upgrade to 1.12.0. There are no known workarounds for these issues.

References: https://github.com/sigstore/cosign/commit/80b79ed8b4d28ccbce3d279fd273606b5cddcc25, https://github.com/sigstore/cosign/security/advisories/GHSA-8gw7-4j42-w388, https://nvd.nist.gov/vuln/detail/CVE-2022-36056