Nvidia model promotion gatekeeper

NVIDIA Model Promotion Gatekeeper

Purpose

Before a NIM container moves from staging to production, prove four things with runtime evidence, then emit a tamper-evident attestation:

1. Signature is valid and from the expected NVIDIA identity — keyless cosign verify against the expected --certificate-identity and --certificate-oidc-issuer.
2. Tag has not drifted — crane digest resolution matches the operator-supplied image_ref@sha256:... pin.
3. SBOM and model card are present and pinned — SPDX or CycloneDX SBOM attestation present; model card present as a fetched OCI referrer with a recorded sha256. A documentation label alone is not enough.
4. No CVE regression vs current-prod — grype delta against the current production digest; new critical or high CVEs block promotion.

The skill never mutates: no docker pull, no kubectl apply, no registry write. It reads, verifies, and emits a JSON attestation the operator signs with cosign sign-blob and hands to audit.

Default mode is dry-run

If the operator does not pass --mode runtime, the skill stays in static mode: it reads supplied fixture or sanitized JSON, runs the gate evaluator, but does not contact any registry or Sigstore endpoint. evidence_level is then documentation-only and verdict defaults to manual-review.

--mode runtime opt-in is per-session, never per-skill-default. The operator must hand the skill an explicit image reference plus a current-prod digest.

Operating rules

• Resolve image_ref → digest via crane digest first. If the operator-supplied pin (image_ref@sha256:...) does not match the resolved digest, emit verdict: block with reason digest_drift.
• The signer identity and OIDC issuer to expect must be supplied as inputs (never defaulted), so a future change in NVIDIA's signing posture cannot silently be auto-accepted.
• Treat any registry prefix other than nvcr.io/ as verdict: block with reason unknown_registry. The allowlist regex enforces this; the skill must also assert it explicitly so the failure mode is auditable.
• Treat a Fulcio cert with notAfter < now as verdict: block with reason expired_cert. A valid-looking signature on an expired cert is a replay artifact.
• Treat missing SBOM attestation as verdict: block with reason missing_sbom. Treat a missing model-card OCI referrer, a label-only model-card reference, or a model-card record without a sha256:... digest as verdict: block with reason missing_model_card.
• Treat a Grype delta showing one or more new CRITICAL or HIGH CVEs vs current_prod_digest as verdict: block with reason cve_regression.
• If Rekor or Fulcio is unreachable (air-gapped or transient), do not auto-block. Emit evidence_level: partial and verdict: manual-review with reason rekor_unreachable. Air-gapped deployments must promote on operator override, not on automatic ignore.
• The attestation must include provenance.executed_commands (exact argv, no env), provenance.egress_hosts_contacted, provenance.runtime_mode, and a 16+ char nonce whenever runtime_mode=runtime. Anti-replay is the operator's responsibility downstream, but the gatekeeper provides the field.
• Never write credentials. Never echo $NGC_API_KEY. The attestation provenance.executed_commands array must scrub any flag values that resemble secrets (no equals-form value capture for --password, --token, --auth).

Required inputs

Field	Required	Example
image_ref	yes	nvcr.io/nim/meta/llama-3.3-70b:1.5.0
image_ref_pin	yes (runtime mode)	sha256:abc123... (operator-supplied expected digest)
current_prod_digest	yes	sha256:def456...
expected_signer_identity	yes	https://github.com/nvidia/nim-builder/.github/workflows/release.yml@refs/tags/v1.5.0
expected_oidc_issuer	yes	https://token.actions.githubusercontent.com
mode	optional	static (default) | runtime

Response shape

The attestation JSON is the canonical response. The agent additionally surfaces, in plain text:

1. Verdict — promote | block | manual-review
2. Evidence level — live | partial | documentation-only
3. Top reasons — verbatim from verdict_reasons[]
4. Next action — cosign sign-blob --bundle attestation.bundle attestation.json for promote; remediation hints for block; explicit operator decision request for manual-review
5. Attestation path — where the JSON was written

References

• references/allowlist-commands.md — exact argv catalog with rationale per command
• references/attestation-format.md — attestation schema walk-through with a worked example