Support nested permissions

Closes: #73
Refs: #75

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## [Unreleased][unreleased]
 
 - Implement metarequire and require nesting
+- Support permissions for node.js modules (including internal but not for npm)
 
 ## [1.1.0][] - 2022-03-15
 

metavm.d.ts

@@ -3,6 +3,8 @@ import { Context, Script, ScriptOptions, BaseOptions } from 'vm';
 export const EMPTY_CONTEXT: Context;
 export const COMMON_CONTEXT: Context;
 
+export class MetavmError extends Error {}
+
 export function createContext(
   context?: Context,
   preventEscape?: boolean
@@ -30,3 +32,10 @@ export function readScript(
   filePath: string,
   options?: BaseOptions
 ): Promise<MetaScript>;
+
+export function metarequire(options: {
+  dirname: string;
+  relative: string;
+  context: Context;
+  access: object;
+}): MetaScript;

metavm.js

@@ -29,6 +29,8 @@ const COMMON_CONTEXT = vm.createContext(
   })
 );
 
+class MetavmError extends Error {}
+
 const createContext = (context, preventEscape = false) => {
   if (context === undefined) return EMPTY_CONTEXT;
   return vm.createContext(context, preventEscape ? CONTEXT_OPTIONS : {});
@@ -60,19 +62,58 @@ const readScript = async (filePath, options) => {
   return script;
 };
 
-const metarequire = (context, permitted = {}) => {
+const internalRequire = require;
+
+const checkAccess = (access, name) => {
+  for (const key of Object.keys(access)) {
+    if (name.startsWith(key)) return Reflect.get(access, key);
+  }
+};
+
+const metarequire = (options) => {
+  const { dirname = process.cwd(), relative = '.' } = options;
+  const context = createContext({ ...options.context });
+  const access = { ...options.access };
+
   const require = (module) => {
-    if (Reflect.has(permitted, module)) {
-      return Reflect.get(permitted, module);
+    let name = module;
+    let lib = checkAccess(access, name);
+    if (lib instanceof Object) return lib;
+    const npm = !name.includes('.');
+    if (!npm) {
+      name = path.resolve(dirname, relative, module);
+      let rel = './' + path.relative(dirname, name);
+      lib = checkAccess(access, rel);
+      if (lib instanceof Object) return lib;
+      const ext = name.toLocaleLowerCase().endsWith('.js') ? '' : '.js';
+      const js = name + ext;
+      name = name.startsWith('.') ? path.resolve(dirname, js) : js;
+      rel = './' + path.relative(dirname, js);
+      lib = checkAccess(access, rel);
+      if (lib instanceof Object) return lib;
     }
+    if (!lib) throw new MetavmError(`Access denied '${module}'`);
     try {
-      const src = fs.readFileSync(module, 'utf8');
+      const absolute = internalRequire.resolve(name);
+      if (npm && absolute === name) return internalRequire(name);
+      let relative = path.dirname(absolute);
+      if (npm) {
+        const dirname = relative;
+        const access = { ...options.access, './': true };
+        relative = '.';
+        context.require = metarequire({ dirname, relative, context, access });
+      } else {
+        context.require = metarequire({ dirname, relative, context, access });
+      }
+      const src = fs.readFileSync(absolute, 'utf8');
       const script = createScript(module, src, { context });
-      return script;
-    } catch {
-      throw new Error(`Cannot find module: '${module}'`);
+      return script.exports;
+    } catch (err) {
+      if (err instanceof MetavmError) throw err;
+      throw new MetavmError(`Cannot find module '${module}'`);
     }
   };
+
   return require;
 };
 

test/examples/nestedmodule1.js

@@ -2,6 +2,6 @@
 ({
   name: 'nestedmodule1',
   value: 1,
-  nested: require('./test/examples/nestedmodule2.js'),
+  nested: require('./nestedmodule2.js'),
 });
 /* eslint-enable */

test/unit.js

@@ -189,7 +189,11 @@ metatests.test('Call undefined as a function', async (test) => {
 metatests.test('Metarequire node internal module', async (test) => {
   const sandbox = {};
   sandbox.global = sandbox;
-  sandbox.require = metavm.metarequire(sandbox, { fs });
+  sandbox.require = metavm.metarequire({
+    dirname: __dirname,
+    sandbox,
+    access: { fs },
+  });
   const context = metavm.createContext(sandbox);
   const src = `({ fs: require('fs') })`;
   const ms = metavm.createScript('Example', src, { context });
@@ -201,41 +205,86 @@ metatests.test('Metarequire node internal module', async (test) => {
 metatests.test('Metarequire internal not permitted', async (test) => {
   const sandbox = {};
   sandbox.global = sandbox;
-  sandbox.require = metavm.metarequire(sandbox);
+  sandbox.require = metavm.metarequire({ dirname: __dirname, sandbox });
   const context = metavm.createContext(sandbox);
   const src = `({ fs: require('fs') })`;
   try {
     const ms = metavm.createScript('Example', src, { context });
     test.strictSame(ms, undefined);
   } catch (err) {
-    test.strictSame(err.message, `Cannot find module: 'fs'`);
+    test.strictSame(err.message, `Access denied 'fs'`);
   }
   test.end();
 });
 
-metatests.test('Metarequire non-existent module', async (test) => {
+metatests.test('Metarequire not permitted module', async (test) => {
   const sandbox = {};
   sandbox.global = sandbox;
-  sandbox.require = metavm.metarequire(sandbox);
+  sandbox.require = metavm.metarequire({ dirname: __dirname, sandbox });
   const context = metavm.createContext(sandbox);
   const src = `({ notExist: require('nothing') })`;
   try {
     const ms = metavm.createScript('Example', src, { context });
     test.strictSame(ms, undefined);
   } catch (err) {
-    test.strictSame(err.message, `Cannot find module: 'nothing'`);
+    test.strictSame(err.message, `Access denied 'nothing'`);
+  }
+  test.end();
+});
+
+metatests.test('Metarequire non-existent module', async (test) => {
+  const sandbox = {};
+  sandbox.global = sandbox;
+  sandbox.require = metavm.metarequire({
+    dirname: __dirname,
+    sandbox,
+    access: { metalog: true },
+  });
+  const context = metavm.createContext(sandbox);
+  const src = `({ notExist: require('metalog') })`;
+  try {
+    const ms = metavm.createScript('Example', src, { context });
+    test.strictSame(ms, undefined);
+  } catch (err) {
+    test.strictSame(err.message, `Cannot find module 'metalog'`);
   }
   test.end();
 });
 
 metatests.test('Metarequire nestsed modules', async (test) => {
   const sandbox = {};
   sandbox.global = sandbox;
-  sandbox.require = metavm.metarequire(sandbox);
+  const access = {
+    './examples/nestedmodule1.js': true,
+    './examples/nestedmodule2.js': true,
+  };
+  sandbox.require = metavm.metarequire({ dirname: __dirname, sandbox, access });
   const context = metavm.createContext(sandbox);
-  const src = `({ loaded: require('./test/examples/nestedmodule1.js') })`;
+  const src = `({ loaded: require('./examples/nestedmodule1.js') })`;
   const ms = metavm.createScript('Example', src, { context });
-  test.strictSame(ms.exports.loaded.exports.value, 1);
-  test.strictSame(ms.exports.loaded.exports.nested.exports.value, 2);
+  test.strictSame(ms.exports.loaded.value, 1);
+  test.strictSame(ms.exports.loaded.nested.value, 2);
+  test.end();
+});
+
+metatests.test('Metarequire nestsed not permitted', async (test) => {
+  const sandbox = {};
+  sandbox.global = sandbox;
+  sandbox.require = metavm.metarequire({
+    dirname: __dirname,
+    sandbox,
+    access: {
+      './examples/nestedmodule1.js': true,
+    },
+  });
+  const context = metavm.createContext(sandbox);
+  const src = `({ loaded: require('./examples/nestedmodule1.js') })`;
+  try {
+    const ms = metavm.createScript('Example', src, { context });
+    test.fail('Should not be loaded', ms);
+  } catch (err) {
+    const module2 = './nestedmodule2.js';
+    test.strictSame(err.message, `Access denied '${module2}'`);
+  }
   test.end();
 });