# atmos plugin sign

Sign an immutable plugin release with Sigstore and publish its signature to OCI.

> ⚠️ Experimental

## Usage

```shell
atmos plugin sign <repository@sha256:digest> [--yes]
```

Atmos validates the published plugin index, signs its exact bytes with a managed Cosign executable,
and attaches the standard Sigstore bundle to that index as an OCI referrer. Registry access uses
the same credentials as other plugin commands. The release digest and version tag remain unchanged.
Tags are not accepted: use the `digest` returned by `atmos plugin publish`.

Signing uses public Sigstore keyless authentication. Locally, Cosign opens its identity-provider login
flow. In supported CI environments, Cosign can obtain the workload identity from the environment;
for GitHub Actions, grant the signing job `id-token: write`. The signer identity and signing event
are recorded in the public transparency log. Signing does not add that identity to consumers'
`trusted_publishers`; consumers configure their own trust policy.

Atmos resolves Cosign through its toolchain and installs it when automatic installation is enabled.
Otherwise, install the selected version first:

```shell
atmos toolchain install sigstore/cosign@3.1.3
```

## Arguments and flags

- **repository@sha256:digest**
  Published plugin release index to sign. An optional 
  oci://
   prefix is accepted.
- **--cosign-version**
  Exact Cosign 3 version managed by the Atmos toolchain. Defaults to 
  3.1.3
  .
- **--yes, -y**
  Accept publication to the Sigstore transparency log without its confirmation prompt. This does not skip identity authentication.
- **--format**
  Output format: table (default), json, yaml, csv, or tsv. Also configurable with 
  ATMOS_PLUGIN_FORMAT
  .

## Examples

Publish and sign in one command:

```shell
atmos plugin publish ./oidc-release --to=oci://ghcr.io/acme/oidc --sign
```

Sign an already published release, or retry after an interrupted signing operation:

```shell
atmos plugin sign ghcr.io/acme/oidc@sha256:<digest> --yes
```

The default output confirms signing and displays the release metadata and immutable
reference. Use `--format json` for structured signed release metadata. If signing or uploading its evidence fails,
the command returns an error. Signing requires network access to Sigstore and the registry.