Rules / GRN-T007

absoluteblockimplemented

GRN-T007 invalid-attestation
Default severity block
Kind absolute rule: fires on the new version alone, whatever the trusted version looked like.
Status Implemented in 0.1

What it checks

An attestation is present for a file of the new version but fails Sigstore verification.

Why it matters

A broken or forged attestation is worse than none: something tried to look trustworthy and failed. Legitimate CI produces attestations that verify.

Example finding

Illustrative; not from a real release.

examplelib 2.6.1 → 2.6.2: BLOCK
  BLOCK GRN-T007 invalid-attestation: 1 attestation(s) in 2.6.2 failed verification
           - examplelib-2.6.2-py3-none-any.whl: signature does not match the file's digest

How to resolve it

  1. Don't install.
  2. Re-run once. A verification failure can come from an outdated Sigstore trust root on your side; upgrading Garnet Guard refreshes it.
  3. If it persists, report it to the project and to the registry's security team (security@pypi.org for PyPI).

Allowlisting

Once you've reviewed a release, ignore this rule for that package and version range. Every ignore needs a reason and an expiry date; after until it stops applying and the report notes that it expired.

[[garnet.ignore]]
package = "examplelib"
versions = "==2.6.2"
rules = ["GRN-T007"]
reason = "registry confirmed a broken attestation upload, see example/examplelib#400"
until = "2027-06-30"
acknowledge_critical = true

GRN-T007 is one of three critical rules (with GRN-K001, GRN-T008). An ignore doesn't apply to it unless it sets acknowledge_critical = true.

To change the rule's severity for every package instead:

[garnet.rules]
"GRN-T007" = "warn"   # "off" | "info" | "warn" | "block"

Suppressed findings still appear in JSON and SARIF output, marked with the ignore that matched. The policy format is in SPEC §7; 0.1's garnet diff doesn't read policy files yet.

See also