Upgrading to Cosign v3

Cosign v3 streamlined its signing workflow by introducing the --bundle flag, replacing the previous approach that required separate certificate and signature files.

What Changed

Previously, signing artifacts with cosign required managing two separate outputs:

• A .pem certificate file via --output-certificate
• A .sig signature file via --output-signature

Now, the --bundle flag combines both into a single .sigstore.json file, simplifying both signing and verification workflows.

Updating Your GoReleaser Configuration

Here's how to update your .goreleaser.yaml:

# https://goreleaser.com/customization/sign
signs:
  - cmd: cosign
-   certificate: "${artifact}.pem"
+   signature: "${artifact}.sigstore.json"
    args:
      - sign-blob
-     - "--output-certificate=${certificate}"
-     - "--output-signature=${signature}"
+     - "--bundle=${signature}"
      - "${artifact}"
      - "--yes"
    artifacts: checksum

The key changes:

1. Remove the certificate field
2. Update signature to use .sigstore.json extension
3. Replace --output-certificate and --output-signature flags with a single --bundle flag

Verifying Signatures

Verification is now simpler too. Instead of:

cosign verify-blob \
  --certificate artifact.pem \
  --signature artifact.sig \
  artifact

You now just need:

cosign verify-blob \
  --bundle artifact.sigstore.json \
  artifact

Try It Out

Check out the complete working example at github.com/goreleaser/example-secure to see the new bundle-based signing in action.

This change reduces complexity and makes artifact signing more straightforward for everyone.

For more details, see goreleaser/goreleaser#6195.