pin-actions

GitHub Actions referenced by mutable tags (@v4) are vulnerable to supply chain attacks — a compromised maintainer can silently move the tag to malicious code. Pinning to a commit SHA makes the reference immutable and tamper-evident.

Script Location

~/.claude/skills/pin-actions/scripts/resolve_action_sha.sh

Interface: ./resolve_action_sha.sh <owner/repo[/path]> <tag> → prints 40-char SHA to stdout

Workflow 1: Scan Mode (pin all unpinned actions in a workflow file)

1. Read the workflow file to identify all uses: lines
2. Filter to unpinned actions — skip:
   • Already-pinned: uses: owner/repo@<40-char hex SHA>
   • Docker-based: uses: docker://...
   • Local actions: uses: ./path/to/action
3. For each unpinned action, extract owner/repo[/subpath] and ref:
   • Pattern: uses: {owner}/{repo}@{ref}
   • Pattern: uses: {owner}/{repo}/{path}@{ref} (sub-path actions)
4. Resolve each SHA using the script:

   SHA=$(~/.claude/skills/pin-actions/scripts/resolve_action_sha.sh "owner/repo" "v4")
   

5. Replace owner/repo@v4 → owner/repo@<SHA> # v4
   • Always preserve the original tag as a trailing comment for human readability

Example transformation

Before:

- uses: actions/checkout@v4
- uses: pnpm/action-setup@v4
- uses: docker/build-push-action/push@v6

After:

- uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
- uses: pnpm/action-setup@a3252b7a1b87b11f31ef2a5405c6fe64a35b06b8 # v4
- uses: docker/build-push-action/push@263435318d21b8e681c14492fe198d362a7d2c83 # v6

Workflow 2: Lookup Mode (resolve a single action on demand)

When asked to look up the SHA for a specific action:

~/.claude/skills/pin-actions/scripts/resolve_action_sha.sh "actions/checkout" "v4"
# → 11bd71901bbe5b1630ceea73d27597364c9af683

Report the SHA and the pinned form:

actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4

Tag Types

The script handles both GitHub tag types transparently:

• Lightweight tags: point directly to a commit (most common for action releases)
• Annotated tags: contain metadata and point to a tag object, which in turn points to a commit — the script dereferences this automatically

Error Handling

If the script exits with code 1, the tag likely doesn't exist for that repo. Verify:

1. Correct owner/repo spelling
2. Tag exists: gh api repos/{owner}/{repo}/git/ref/tags/{tag}
3. The repo has releases (not all action repos use tags)