## Problem
GitHub SLSA provenance attestations have been silently failing on
**every release** since they were introduced. Confirmed across all 10+
release runs checked (v2.29.2 through v2.31.6).
The `actions/attest` action requires `subject-digest` (a `sha256:...`
hash) to identify the artifact being attested, but the workflow only
provided `subject-name` (the image tag like
`ghcr.io/coder/coder:v2.31.6`). This caused every attestation step to
error with:
```
Error: One of subject-path, subject-digest, or subject-checksums must be provided
```
The failures were masked by `continue-on-error: true` and only surfaced
as `##[warning]` annotations that nobody noticed. Enterprise customers
doing `gh attestation verify` would find no provenance records for any
of our Docker images.
> [!NOTE]
> The cosign SBOM attestation (separate step) has been working correctly
the entire time — it uses a different mechanism (`cosign attest --type
spdxjson`) that does not require the same inputs. This fix is
specifically for the GitHub-native SLSA provenance attestations.
## Fix
**Add `subject-digest` to all `actions/attest` steps** (release.yaml +
ci.yaml):
- Base image: capture digest from `depot/build-push-action` output
- Main image: resolve digest via `docker buildx imagetools inspect
--raw` after push
- Latest image: same approach
- Use `subject-name` without tag per the [actions/attest
docs](https://github.com/actions/attest#container-image)
**Update `anchore/sbom-action`** from v0.18.0 to v0.24.0 (node24
support, ahead of the [June 2
deadline](https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/)).
All changes remain non-blocking for the release process
(`continue-on-error: true` preserved).
> 🤖 This PR was created with the help of Coder Agents, and is reviewed
by a human.
This pull request adds new GitHub Actions for installing `cosign` and
`syft`, and updates the CI, release, and security workflows.
**New Actions:**
- [`install-cosign`](.github/actions/install-cosign/action.yaml):
Installs `cosign` with a configurable version.
- [`install-syft`](.github/actions/install-syft/action.yaml): Installs
`syft` with a configurable version.
**Workflow Updates:**
- CI, release, and security workflows now use `install-cosign` and
`install-syft`.
Atif Ali