process: make source map getter resistant against prototype tampering

Since this code runs during process and Worker shutdown, it should not
call user-provided code and thereby e.g. provide a way to break out of
`worker.terminate()`.

PR-URL: #30228
Reviewed-By: Joyee Cheung <[email protected]>
Reviewed-By: Ben Coe <[email protected]>
Reviewed-By: Michaël Zasso <[email protected]>
Reviewed-By: James M Snell <[email protected]>

lib/internal/source_map/source_map_cache.js

@@ -1,5 +1,28 @@
 'use strict';
 
+const {
+  JSON,
+  Object: {
+    create: ObjectCreate,
+    keys: ObjectKeys,
+    getOwnPropertyDescriptor: ObjectGetOwnPropertyDescriptor,
+  },
+  ObjectPrototype: {
+    hasOwnProperty: ObjectHasOwnProperty
+  },
+  MapPrototype: {
+    entries: MapEntries
+  }, uncurryThis
+} = primordials;
+
+const MapIteratorNext = uncurryThis(MapEntries(new Map()).next);
+const WeakMapGet = uncurryThis(WeakMap.prototype.get);
+
+function ObjectGetValueSafe(obj, key) {
+  const desc = ObjectGetOwnPropertyDescriptor(obj, key);
+  return ObjectHasOwnProperty(desc, 'value') ? desc.value : undefined;
+}
+
 // See https://sourcemaps.info/spec.html for SourceMap V3 specification.
 const { Buffer } = require('buffer');
 const debug = require('internal/util/debuglog').debuglog('source_map');
@@ -9,14 +32,14 @@ const { getOptionValue } = require('internal/options');
 const {
   normalizeReferrerURL,
 } = require('internal/modules/cjs/helpers');
-const { JSON, Object } = primordials;
 // For cjs, since Module._cache is exposed to users, we use a WeakMap
 // keyed on module, facilitating garbage collection.
 const cjsSourceMapCache = new WeakMap();
 // The esm cache is not exposed to users, so we can use a Map keyed
 // on filenames.
 const esmSourceMapCache = new Map();
 const { fileURLToPath, URL } = require('url');
+let Module;
 
 let experimentalSourceMaps;
 function maybeCacheSourceMap(filename, content, cjsModuleInstance) {
@@ -40,6 +63,7 @@ function maybeCacheSourceMap(filename, content, cjsModuleInstance) {
     const data = dataFromUrl(basePath, match.groups.sourceMappingURL);
     const url = data ? null : match.groups.sourceMappingURL;
     if (cjsModuleInstance) {
+      if (!Module) Module = require('internal/modules/cjs/loader').Module;
       cjsSourceMapCache.set(cjsModuleInstance, {
         filename,
         lineLengths: lineLengths(content),
@@ -148,17 +172,27 @@ function rekeySourceMap(cjsModuleInstance, newInstance) {
   }
 }
 
+// WARNING: The `sourceMapCacheToObject` and `appendCJSCache` run during
+// shutdown. In particular, they also run when Workers are terminated, making
+// it important that they do not call out to any user-provided code, including
+// built-in prototypes that might have been tampered with.
+
 // Get serialized representation of source-map cache, this is used
 // to persist a cache of source-maps to disk when NODE_V8_COVERAGE is enabled.
 function sourceMapCacheToObject() {
-  const obj = Object.create(null);
+  const obj = ObjectCreate(null);
 
-  for (const [k, v] of esmSourceMapCache) {
+  const it = MapEntries(esmSourceMapCache);
+  let entry;
+  while (!(entry = MapIteratorNext(it)).done) {
+    const k = entry.value[0];
+    const v = entry.value[1];
     obj[k] = v;
   }
+
   appendCJSCache(obj);
 
-  if (Object.keys(obj).length === 0) {
+  if (ObjectKeys(obj).length === 0) {
     return undefined;
   } else {
     return obj;
@@ -171,23 +205,28 @@ function sourceMapCacheToObject() {
 // TODO(bcoe): this means we don't currently serialize source-maps attached
 // to error instances, only module instances.
 function appendCJSCache(obj) {
-  const { Module } = require('internal/modules/cjs/loader');
-  Object.keys(Module._cache).forEach((key) => {
-    const value = cjsSourceMapCache.get(Module._cache[key]);
+  if (!Module) return;
+  const cjsModuleCache = ObjectGetValueSafe(Module, '_cache');
+  const cjsModules = ObjectKeys(cjsModuleCache);
+  for (let i = 0; i < cjsModules.length; i++) {
+    const key = cjsModules[i];
+    const module = ObjectGetValueSafe(cjsModuleCache, key);
+    const value = WeakMapGet(cjsSourceMapCache, module);
     if (value) {
+      // This is okay because `obj` has a null prototype.
       obj[`file://${key}`] = {
-        lineLengths: value.lineLengths,
-        data: value.data,
-        url: value.url
+        lineLengths: ObjectGetValueSafe(value, 'lineLengths'),
+        data: ObjectGetValueSafe(value, 'data'),
+        url: ObjectGetValueSafe(value, 'url')
       };
     }
-  });
+  }
 }
 
 // Attempt to lookup a source map, which is either attached to a file URI, or
 // keyed on an error instance.
 function findSourceMap(uri, error) {
-  const { Module } = require('internal/modules/cjs/loader');
+  if (!Module) Module = require('internal/modules/cjs/loader').Module;
   let sourceMap = cjsSourceMapCache.get(Module._cache[uri]);
   if (!uri.startsWith('file://')) uri = normalizeReferrerURL(uri);
   if (sourceMap === undefined) {

test/parallel/test-worker-terminate-source-map.js

@@ -0,0 +1,40 @@
+'use strict';
+const common = require('../common');
+const tmpdir = require('../common/tmpdir');
+const assert = require('assert');
+
+// Attempts to test that the source map JS code run on process shutdown
+// does not call any user-defined JS code.
+
+const { Worker, workerData, parentPort } = require('worker_threads');
+
+if (!workerData) {
+  tmpdir.refresh();
+  process.env.NODE_V8_COVERAGE = tmpdir.path;
+
+  // Count the number of some calls that should not be made.
+  const callCount = new Int32Array(new SharedArrayBuffer(4));
+  const w = new Worker(__filename, { workerData: { callCount } });
+  w.on('message', common.mustCall(() => w.terminate()));
+  w.on('exit', common.mustCall(() => {
+    assert.strictEqual(callCount[0], 0);
+  }));
+  return;
+}
+
+const { callCount } = workerData;
+
+function increaseCallCount() { callCount[0]++; }
+
+// Increase the call count when a forbidden method is called.
+Object.getPrototypeOf((new Map()).entries()).next = increaseCallCount;
+Map.prototype.entries = increaseCallCount;
+Object.keys = increaseCallCount;
+Object.create = increaseCallCount;
+Object.hasOwnProperty = increaseCallCount;
+Object.defineProperty(Object.prototype, 'value', {
+  get: increaseCallCount,
+  set: increaseCallCount
+});
+
+parentPort.postMessage('done');