ci: scan the release and main binaries with trivy

.github/trivyignore

@@ -0,0 +1,3 @@
+# Advisories triaged out of main-binary-scan.yaml, one ID per line with the reason above it. Findings with
+# no fixed version are already skipped by the workflow, so this is only for fixable findings in code the
+# binary never calls. Remove an entry once the dependency moves past it.

.github/workflows/main-binary-scan.yaml

@@ -0,0 +1,65 @@
+---
+# Scans the binaries for known vulnerabilities via the Go module and stdlib versions they embed. Two jobs so
+# the red X on main says what to do: `release` scans the last published release (what users are running, so
+# red means cut a release) and `main` scans a fresh build of this commit (what the next release would ship,
+# so red means bump the dependency). govulncheck (pr-govulncheck.yaml) is the reachability check on PRs;
+# this is the version-based artifact check, the same shape as hashicorp's release security scan.
+name: binary vulnerability scan
+on:
+  push:
+    branches: [ 'main' ]
+  schedule:
+    - cron: '23 5 * * 1' # weekly, so new advisories against unchanged binaries still turn main red
+  workflow_dispatch: # release.yaml reruns the failed jobs of the latest run on main once a release publishes
+
+permissions:
+  contents: read
+
+jobs:
+  release:
+    name: release binary
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - name: Download the latest release
+        env:
+          GH_TOKEN: ${{ github.token }}
+          GH_REPO: ${{ github.repository }}
+        run: |
+          gh release download --pattern '*linux_amd64.tar.gz' --dir release
+          tar -xzf release/*.tar.gz -C release
+          rm release/*.tar.gz
+      # rootfs, not fs: fs mode does not read go binaries. unfixed findings are skipped because nothing can
+      # clear them; anything else triaged out goes in .github/trivyignore with a reason
+      - uses: aquasecurity/trivy-action@ed142fd0673e97e23eac54620cfb913e5ce36c25 # v0.36.0
+        with:
+          scan-type: rootfs
+          scan-ref: release
+          scanners: vuln
+          severity: HIGH,CRITICAL
+          ignore-unfixed: true
+          trivyignores: .github/trivyignore
+          exit-code: 1
+
+  main:
+    name: build of main
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          persist-credentials: false
+      - uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e # v7.0.0
+        with:
+          go-version-file: ./.go-version
+      - run: go build -o out/terrafmt .
+      - uses: aquasecurity/trivy-action@ed142fd0673e97e23eac54620cfb913e5ce36c25 # v0.36.0
+        with:
+          scan-type: rootfs
+          scan-ref: out
+          scanners: vuln
+          severity: HIGH,CRITICAL
+          ignore-unfixed: true
+          trivyignores: .github/trivyignore
+          exit-code: 1

.github/workflows/release.yaml

@@ -63,3 +63,24 @@ jobs:
           TAG: ${{ github.ref_name }}
           HOMEBREW_TAP_GITHUB_TOKEN: ${{ secrets.HOMEBREW_TAP_GITHUB_TOKEN }}
         run: ./scripts/update-homebrew-formula.sh
+
+  # the binary scan (main-binary-scan.yaml) goes red on main when the published release has a known
+  # vulnerability, and only a release can clear it. rerun the failed jobs of the scan runs on main's head so
+  # the red check runs are replaced in place; a fresh run from a new event would sit beside them and the
+  # commit would stay red
+  rescan:
+    needs: goreleaser
+    runs-on: ubuntu-latest
+    permissions:
+      actions: write # rerun workflow jobs
+    steps:
+      - name: rerun the failed binary scan jobs on main
+        env:
+          GH_TOKEN: ${{ github.token }}
+          GH_REPO: ${{ github.repository }}
+        run: |
+          head=$(gh api "repos/$GH_REPO/commits/main" --jq .sha)
+          runs=$(gh run list -w main-binary-scan.yaml -c "$head" --json databaseId,conclusion \
+            --jq '.[] | select(.conclusion == "failure") | .databaseId')
+          if [ -z "$runs" ]; then echo "no failed binary scan on main ($head), nothing to rerun"; exit 0; fi
+          for run in $runs; do echo "rerunning failed jobs of $run"; gh run rerun "$run" --failed; done