Harden input interpolation and pin binfmt image#2
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Pass action inputs through env vars instead of interpolating
${{ inputs.* }} directly into run: shell bodies, closing the
script-injection path flagged by GitHub's hardening guidance.
The App token likewise moves to an env var so it is no longer
baked into the NIX_CONFIG script text.
Also pin the tonistiigi/binfmt image (was implicit :latest) and
add a checkout opt-out to update-flake, matching the CI action.
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What
Hardens both composite actions against shell script injection and removes a couple of supply-chain / ergonomics gaps surfaced in a review.
Changes
action.yml) — every${{ inputs.* }}that was expanded directly into arun:shell body now flows through anenv:block and is referenced as a quoted shell variable (TRUST_FLAKE,EMULATE_SYSTEMS,FLAKE_CHECK_ARGS,BUILD_HOSTS,BUILD_DEVSHELLS,BUILD_ATTRS,BUILD_ARGS,MATRIX_NAME,CHECKS,HEAD_SHA,DEVSHELL). Follows GitHub's hardening guidance: composite-action inputs can carry untrusted data, so they should never be interpolated into run steps. Word-splitting behavior for the args inputs is preserved.APP_TOKENenv var instead of being interpolated into the NIX_CONFIG script text.tonistiigi/binfmt— was implicit:latest, nowtonistiigi/binfmt:qemu-v9.2.2.update-flakecheckout opt-out — added acheckoutinput (default"true") gating the checkout step, matching the CI action; documented in the README.Verification
${{ ... }}remains inside anyrun:body (survivors are all inwith:/env:/value:/action fields).No behavior change for existing callers. Third-party actions were all already on current major versions, so no version bumps were needed.