ci: pin third-party GitHub Actions to commit SHAs#372
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Pin all external GitHub Actions to immutable commit SHAs (with a trailing version comment) rather than mutable version tags, following GitHub's security-hardening guidance. A mutable tag such as @v6 can be retargeted at malicious code if the action's repository is compromised (as in the March 2025 tj-actions/changed-files incident); a full commit SHA is immutable, so each run is reproducible and immune to tag-move attacks. Also add a 7-day Dependabot cooldown so action updates aren't picked up until they have been published for a week. Dependabot continues to maintain the pins, bumping both the SHA and the version comment. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Self-merging. We only use official GitHub Actions in this repository, so the actual risk is low; this is more about establishing the convention. |
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Summary
Hardens CI supply-chain security by pinning all external GitHub Actions to immutable commit SHAs instead of mutable version tags, and adds a Dependabot cooldown. This mirrors enthought/envisage#604.
Why
A
uses: owner/repo@v6reference resolves through a mutable git tag. If an attacker compromises an action's repository — or just gains the ability to move a tag — they can retargetv6at malicious code, and every workflow pinned to that tag runs it on the next CI run, with access to that job's secrets. This is what happened in the March 2025tj-actions/changed-filescompromise, where version tags were retroactively moved to a commit that exfiltrated CI secrets. Full-SHA pins are immutable, so each run is reproducible and immune to tag-move attacks. Follows GitHub's security-hardening guidance.Changes
Pin all external actions to commit SHAs with a trailing version comment:
actions/checkoutdf4cb1cactions/setup-pythonece7cb0actions/cache55cc834enthought/setup-edm-actione68a4e0Add a 7-day Dependabot cooldown (
cooldown: default-days: 7) so action updates aren't picked up until they've been published for a week, reducing exposure to a compromised release that gets yanked shortly after publication.Dependabot continues to maintain the SHA pins, bumping both the SHA and the version comment. The pinned versions match what apptools already used (checkout/setup-python/cache v6, setup-edm-action v4.2); this change is functionally a no-op beyond the pinning itself.
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