fix: least-privilege workflow token permissions

.github/workflows/cleanup-orphaned-workflows.yml

@@ -14,7 +14,6 @@ on:
       - "scripts/cleanup-orphaned-workflows.mjs"
 
 permissions:
-  actions: write
   contents: read
 
 concurrency:
@@ -26,6 +25,9 @@ jobs:
     name: Delete orphaned workflow runs
     runs-on: ubuntu-latest
     timeout-minutes: 10
+    permissions:
+      actions: write
+      contents: read
     steps:
       - name: Check out trusted default-branch code
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1

scripts/lib/workflow-security.mjs

@@ -68,6 +68,19 @@ export function validateWorkflowFile(path, source) {
 
   const allowedWrites = WRITE_ALLOWLIST.get(path) || new Set();
   for (const write of facts.permissionWrites) {
+    if (write.topLevel) {
+      errors.push(
+        error(
+          "top_level_write_forbidden",
+          path,
+          write.line,
+          write.writeAll
+            ? "Top-level write-all is forbidden; keep top-level permissions read-only and declare writes at the job level."
+            : `Top-level ${write.permission}: write is forbidden; keep top-level permissions read-only and declare writes at the job level.`,
+        ),
+      );
+      continue;
+    }
     if (write.writeAll) {
       errors.push(
         error("write_all_forbidden", path, write.line, "write-all is forbidden."),

scripts/lib/workflow-yaml-security.mjs

@@ -237,7 +237,7 @@ export function workflowSecurityFacts(source = "") {
     if (row.key === "permissions") {
       if (row.indent === 0) facts.topLevelPermissions.push(row);
       if (row.value === "write-all") {
-        facts.permissionWrites.push({ permission: "*", line: row.line, writeAll: true });
+        facts.permissionWrites.push({ permission: "*", line: row.line, writeAll: true, topLevel: row.indent === 0 });
       } else if (/^\{.*\}$/.test(row.value)) {
         const body = row.value.slice(1, -1);
         for (const item of body.split(",")) {
@@ -246,13 +246,13 @@ export function workflowSecurityFacts(source = "") {
           const permission = decodeScalar(pair[0]);
           const value = decodeScalar(pair[1]);
           if (value === "write") {
-            facts.permissionWrites.push({ permission, line: row.line, writeAll: false });
+            facts.permissionWrites.push({ permission, line: row.line, writeAll: false, topLevel: row.indent === 0 });
           }
         }
       } else if (!row.value) {
         for (const child of descendants(parsed.records, index)) {
           if (child.value === "write") {
-            facts.permissionWrites.push({ permission: child.key, line: child.line, writeAll: false });
+            facts.permissionWrites.push({ permission: child.key, line: child.line, writeAll: false, topLevel: row.indent === 0 });
           }
         }
       }

tests/unit/workflow-security.test.mjs

@@ -117,15 +117,15 @@ test("quoted YAML keys cannot bypass pull_request_target or write checks", () =>
   const source = `name: Bad\n'on':\n  'pull_request_target':\n'permissions':\n  'contents': write\njobs:\n  test:\n    runs-on: ubuntu-latest\n    steps:\n      - 'uses': 'actions/checkout@v6'\n`;
   const errors = validateWorkflowFile(".github/workflows/bad.yml", source);
   assert(errors.some((error) => error.code === "pull_request_target_forbidden"));
-  assert(errors.some((error) => error.code === "write_permission_not_allowed"));
+  assert(errors.some((error) => error.code === "top_level_write_forbidden" || error.code === "write_permission_not_allowed"));
   assert(errors.some((error) => error.code === "action_not_pinned"));
 });
 
 test("inline trigger and permissions mappings are inspected semantically", () => {
   const source = `name: Bad\non: [push, 'pull_request_target']\npermissions: { contents: write }\njobs:\n  test:\n    runs-on: ubuntu-latest\n`;
   const errors = validateWorkflowFile(".github/workflows/bad.yml", source);
   assert(errors.some((error) => error.code === "pull_request_target_forbidden"));
-  assert(errors.some((error) => error.code === "write_permission_not_allowed"));
+  assert(errors.some((error) => error.code === "top_level_write_forbidden" || error.code === "write_permission_not_allowed"));
 });
 
 test("unsupported YAML indirection fails closed", () => {
@@ -150,11 +150,24 @@ test("accepts checkout only when its own step disables credential persistence",
 });
 
 test("rejects write permissions outside approved workflows", () => {
-  const source = `name: Bad\non:\n  push:\npermissions:\n  contents: write\njobs:\n  test:\n    runs-on: ubuntu-latest\n    steps:\n      - uses: actions/checkout@${"a".repeat(40)}\n        with:\n          persist-credentials: false\n`;
+  const source = `name: Bad\non:\n  push:\npermissions:\n  contents: read\njobs:\n  test:\n    runs-on: ubuntu-latest\n    permissions:\n      contents: write\n    steps:\n      - uses: actions/checkout@${"a".repeat(40)}\n        with:\n          persist-credentials: false\n`;
   const errors = validateWorkflowFile(".github/workflows/bad.yml", source);
   assert(errors.some((error) => error.code === "write_permission_not_allowed"));
 });
 
+test("rejects top-level write permissions even on allowlisted workflows", () => {
+  const source = `name: Clean\non:\n  push:\npermissions:\n  actions: write\n  contents: read\njobs:\n  cleanup:\n    runs-on: ubuntu-latest\n    steps:\n      - uses: actions/checkout@${"a".repeat(40)}\n        with:\n          persist-credentials: false\n`;
+  const errors = validateWorkflowFile(".github/workflows/cleanup-orphaned-workflows.yml", source);
+  assert(errors.some((error) => error.code === "top_level_write_forbidden"));
+});
+
+test("accepts job-level write permissions on allowlisted workflows", () => {
+  const source = `name: Clean\non:\n  push:\npermissions:\n  contents: read\njobs:\n  cleanup:\n    runs-on: ubuntu-latest\n    permissions:\n      actions: write\n      contents: read\n    steps:\n      - uses: actions/checkout@${"a".repeat(40)}\n        with:\n          persist-credentials: false\n`;
+  const errors = validateWorkflowFile(".github/workflows/cleanup-orphaned-workflows.yml", source);
+  assert.equal(errors.some((error) => error.code === "top_level_write_forbidden"), false);
+  assert.equal(errors.some((error) => error.code === "write_permission_not_allowed"), false);
+});
+
 test("desired repository policy is fail-closed", () => {
   const policy = desiredPolicy();
   assert.deepEqual(validateRepositoryPolicy(policy), []);