chore(ci): harden workflows, enforce zizmor

.github/workflows/broker-audit.yml

@@ -24,6 +24,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v7
+        with:
+          persist-credentials: true  # this workflow pushes with the checkout's credentials
 
       - uses: actions/setup-go@v7
         with:
@@ -39,7 +41,7 @@ jobs:
         run: go run ./cmd/eraser validate-brokers data/brokers.yaml
 
       - name: Open prune PR if anything changed
-        uses: peter-evans/create-pull-request@v8
+        uses: peter-evans/create-pull-request@5f6978faf089d4d20b00c7766989d076bb2fc7f1 # v8.1.1
         with:
           branch: broker-audit/prune
           base: main

.github/workflows/ci.yml

@@ -15,18 +15,27 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true
 
+# Read-only token; no job here writes to the repo or reads other scopes.
+permissions:
+  contents: read
+
 jobs:
   ci:
     uses: drumandbytes/reusable-actions/.github/workflows/go-ci.yml@v1
     with:
       test-race: true
 
+  # Audit of this repo's own workflows; accepted findings are in
+  # .github/zizmor.yml.
+  zizmor:
+    uses: drumandbytes/reusable-actions/.github/workflows/zizmor.yml@v1
+
   # Single stable name for the org's required-status-check ruleset to point
   # at, regardless of how the real jobs above are split or renamed.
   required-checks-passed:
     name: Required checks passed
     runs-on: ubuntu-latest
-    needs: [ci]
+    needs: [ci, zizmor]
     if: always()
     steps:
       - if: contains(needs.*.result, 'failure') || contains(needs.*.result, 'cancelled')

.github/workflows/deploy.yaml

@@ -35,12 +35,18 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
 
+      # No module cache in a deploy job: a cache written by another ref could
+      # end up in what gets published. The Go step here only generates site
+      # content, so the cold fetch costs little.
       - uses: actions/setup-go@v7
         with:
           go-version: "1.26"
+          cache: false
 
-      - uses: peaceiris/actions-hugo@v3
+      - uses: peaceiris/actions-hugo@2752ce1d29631191ea3f27c23495fa06139a5b78 # v3.2.1
         with:
           hugo-version: "0.165.0"
 
@@ -53,7 +59,7 @@ jobs:
       - name: Build
         run: hugo --minify --source site
 
-      - uses: cloudflare/wrangler-action@v4
+      - uses: cloudflare/wrangler-action@25853364521e0d392ece9b0c1e97a4b37b638087 # v4.1.2
         with:
           apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}
           accountId: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}

.github/workflows/release.yml

@@ -16,21 +16,16 @@ jobs:
     steps:
       - uses: actions/checkout@v7
         with:
+          persist-credentials: false
           fetch-depth: 0 # full history + tags for the changelog and git describe
 
+      # No caches in the release build: a cache written by another ref could
+      # be restored into the published binaries. Releases are rare, so the
+      # cold build is the cheaper side of that trade.
       - uses: actions/setup-go@v7
         with:
           go-version: "1.26"
-          # setup-go caches the module cache; add the build cache ourselves,
-          # keyed on the toolchain + deps + release config. Cross-compiling
-          # six targets from a cold build cache is most of the run time.
-      - uses: actions/cache@v6
-        with:
-          path: ~/.cache/go-build
-          key: ${{ runner.os }}-go-build-release-${{ hashFiles('go.sum', '.goreleaser.yaml') }}
-          restore-keys: |
-            ${{ runner.os }}-go-build-release-
-            ${{ runner.os }}-go-build-
+          cache: false
 
       # Short-lived token for the dnb-robot GitHub App, scoped to this repo (to
       # publish the release) and homebrew-tap (for GoReleaser to push the
@@ -40,10 +35,12 @@ jobs:
         with:
           client-id: ${{ secrets.DNB_ROBOT_CLIENT_ID }}
           private-key: ${{ secrets.AUTOMATION_APP_PRIVATE_KEY }}
+          # Only what this job needs (goreleaser publishes the release and pushes the cask to homebrew-tap), not the app's whole grant.
+          permission-contents: write
           owner: drumandbytes
           repositories: eraser,homebrew-tap
 
-      - uses: goreleaser/goreleaser-action@v7
+      - uses: goreleaser/goreleaser-action@f06c13b6b1a9625abc9e6e439d9c05a8f2190e94 # v7.2.3
         with:
           version: "~> v2"
           args: release --clean

.github/zizmor.yml

@@ -0,0 +1,18 @@
+# zizmor configuration, read by the zizmor job in ci.yml. Anything accepted
+# here is accepted on purpose -- each entry says why.
+
+rules:
+  unpinned-uses:
+    config:
+      policies:
+        # GitHub's own and the org's actions stay on tags (Dependabot moves
+        # them); third-party actions are SHA-pinned.
+        "actions/*": ref-pin
+        "drumandbytes/*": ref-pin
+        "*": hash-pin
+
+  dangerous-triggers:
+    ignore:
+      # workflow_run so Dependabot PRs get a token that can merge; never
+      # checks out PR code.
+      - auto-merge.yml