Only Images Somebody Vouched For Get to Run

gcp-binary-authorization

Only images somebody vouched for get to run. Works with Terraform and OpenTofu (>= 1.6), google provider >= 6.0, < 7.0.

enforcement_mode = DRYRUN_AUDIT_LOG_ONLY admits the image and writes a line about it. The policy is attached, the console shows it as configured, the audit log fills with violations - and the unsigned image is running in production the whole time. Dry run is the right way to introduce this policy and the wrong way to leave it.

evaluation_mode = ALWAYS_ALLOW is the other way to have nothing. It is a valid, enforced policy that admits everything, so the enforcement mode can be entirely correct and the policy still check nothing at all. Both have to be right, which is why actually_blocks is a single output over both rather than two you have to combine yourself.

admission_whitelist_patterns are exemptions, and a wildcard is a blanket one. Patterns like gcr.io/my-project/base/* are how base images and sidecars get in; a pattern of * admits every image from everywhere while the policy still reports as enforcing. A precondition refuses it.

global_policy_evaluation_mode = ENABLE also admits Google-maintained images without your attestations. That is usually wanted, because system containers have to start - but it is a set of images you did not sign and did not list, and it is worth knowing it is there.

Smaller things: a precondition refuses REQUIRE_ATTESTATION with no attestors, which would block every deployment rather than none; and clusters_not_enforcing lists per-cluster overrides that admit unsigned images regardless of what the default rule says, since a dev-cluster exception is exactly the kind of thing that quietly outlives its reason.

Verification

Static validation runs tofu fmt, init, validate, tflint and checkov. This module has not yet had a live test, so it is published as statically validated with its live test pending and does not carry the live-tested mark.