Container image provenance with Cosign in GitLab CI/CD

This post introduces and demonstrates the integration of Cosign with GitLab CI/CD for container image provenance. It provides a detailed `.gitlab-ci.yml` example that automates building Docker images, signing them with Cosign using keyless signing via OIDC tokens, and annotating them with build metadata (user, pipeline, job, commit details). It also includes a verification step to ensure the integrity of the signature and annotations. The post explains the benefits of image signing and annotation for software supply chain security and DevSecOps.