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‼️ Project Discontinued ‼️

TL;DR The library contains critical security issues and should not be used for production! The maintenance of the project has been discontinued. Consider migrating your code to isolated-vm.

Dear community,

It's been a truly remarkable journey for me since the vm2 project started nine years ago. The original intent was to devise a method for running untrusted code in Node, with a keen focus on maintaining in-process performance. Proxies, an emerging feature in JavaScript at that time, became our tool of choice for this task.

From the get-go, we recognized the arduous task that lay ahead, as we tried to safeguard against the myriad of escape scenarios JavaScript presented. However, the thrill of the chase kept us going, hopeful that we could overcome these hurdles.

Through the years, this project has seen numerous contributions from passionate individuals. I wish to extend my deepest gratitude to all of you. Special thanks go to @XmiliaH, whose unwavering dedication in maintaining and improving this library over the last 4 years was instrumental to its sustained relevance.

Unfortunately, the growing complexity of Node has brought us to a crossroads. We now find ourselves facing an escape so complicated that fixing it seems impossible. And this isn't about one isolated issue. Recent reports have highlighted that sustaining this project in its current form is not viable in the long term.

Therefore, we must announce the discontinuation of this project.

You may wonder, "What now?"

While this may seem like an end, I see it as an opportunity for you to transition your projects and adapt to a new solution. We would recommend migrating your code to the isolated-vm, a library which employs a slightly different, yet equally effective, approach to sandboxing untrusted code.

Thank you all for your support and understanding during this journey.

Warm Regards, Patrik Simek

<details> <summary>The original Readme is available here.</summary>

vm2 is a sandbox that can run untrusted code with whitelisted Node's built-in modules. Securely!

Features

How does it work

What is the difference between Node's vm and vm2?

Try it yourself:

const vm = require('vm');
vm.runInNewContext('this.constructor.constructor("return process")().exit()');
console.log('Never gets executed.');

const {VM} = require('vm2');
new VM().run('this.constructor.constructor("return process")().exit()');
// Throws ReferenceError: process is not defined

Installation

IMPORTANT: VM2 requires Node.js 6 or newer.

npm install vm2

Quick Example

const {VM} = require('vm2');
const vm = new VM();

vm.run(`process.exit()`); // TypeError: process.exit is not a function

const {NodeVM} = require('vm2');
const vm = new NodeVM({
    require: {
        external: true,
        root: './'
    }
});

vm.run(`
    var request = require('request');
    request('http://www.google.com', function (error, response, body) {
        console.error(error);
        if (!error && response.statusCode == 200) {
            console.log(body); // Show the HTML for the Google homepage.
        }
    });
`, 'vm.js');

Documentation

VM

VM is a simple sandbox to synchronously run untrusted code without the require feature. Only JavaScript built-in objects and Node's Buffer are available. Scheduling functions (setInterval, setTimeout and setImmediate) are not available by default.

Options:

IMPORTANT: Timeout is only effective on synchronous code that you run through run. Timeout does NOT work on any method returned by VM. There are some situations when timeout doesn't work - see #244.

const {VM} = require('vm2');

const vm = new VM({
    timeout: 1000,
    allowAsync: false,
    sandbox: {}
});

vm.run('process.exit()'); // throws ReferenceError: process is not defined

You can also retrieve values from VM.

let number = vm.run('1337'); // returns 1337

TIP: See tests for more usage examples.

NodeVM

Unlike VM, NodeVM allows you to require modules in the same way that you would in the regular Node's context.

Options:

IMPORTANT: Timeout is not effective for NodeVM so it is not immune to while (true) {} or similar evil.

REMEMBER: The more modules you allow, the more fragile your sandbox becomes.

const {NodeVM} = require('vm2');

const vm = new NodeVM({
    console: 'inherit',
    sandbox: {},
    require: {
        external: true,
        builtin: ['fs', 'path'],
        root: './',
        mock: {
            fs: {
                readFileSync: () => 'Nice try!'
            }
        }
    }
});

// Sync

let functionInSandbox = vm.run('module.exports = function(who) { console.log("hello "+ who); }');
functionInSandbox('world');

// Async

let functionWithCallbackInSandbox = vm.run('module.exports = function(who, callback) { callback("hello "+ who); }');
functionWithCallbackInSandbox('world', (greeting) => {
    console.log(greeting);
});

When wrapper is set to none, NodeVM behaves more like VM for synchronous code.

assert.ok(vm.run('return true') === true);

TIP: See tests for more usage examples.

Loading modules by relative path

To load modules by relative path, you must pass the full path of the script you're running as a second argument to vm's run method if the script is a string. The filename is then displayed in any stack traces generated by the script.

vm.run('require("foobar")', '/data/myvmscript.js');

If the script you are running is a VMScript, the path is given in the VMScript constructor.

const script = new VMScript('require("foobar")', {filename: '/data/myvmscript.js'});
vm.run(script);

Resolver

A resolver can be created via makeResolverFromLegacyOptions and be used for multiple NodeVM instances allowing to share compiled module code potentially speeding up load times. The first example of NodeVM can be rewritten using makeResolverFromLegacyOptions as follows.

const resolver = makeResolverFromLegacyOptions({
    external: true,
    builtin: ['fs', 'path'],
    root: './',
    mock: {
        fs: {
            readFileSync: () => 'Nice try!'
        }
    }
});
const vm = new NodeVM({
    console: 'inherit',
    sandbox: {},
    require: resolver
});

VMScript

You can increase performance by using precompiled scripts. The precompiled VMScript can be run multiple times. It is important to note that the code is not bound to any VM (context); rather, it is bound before each run, just for that run.

const {VM, VMScript} = require('vm2');

const vm = new VM();
const script = new VMScript('Math.random()');
console.log(vm.run(script));
console.log(vm.run(script));

It works for both VM and NodeVM.

const {NodeVM, VMScript} = require('vm2');

const vm = new NodeVM();
const script = new VMScript('module.exports = Math.random()');
console.log(vm.run(script));
console.log(vm.run(script));

Code is compiled automatically the first time it runs. One can compile the code anytime with script.compile(). Once the code is compiled, the method has no effect.

Error handling

Errors in code compilation and synchronous code execution can be handled by try-catch. Errors in asynchronous code execution can be handled by attaching uncaughtException event handler to Node's process.

try {
    var script = new VMScript('Math.random()').compile();
} catch (err) {
    console.error('Failed to compile script.', err);
}

try {
    vm.run(script);
} catch (err) {
    console.error('Failed to execute script.', err);
}

process.on('uncaughtException', (err) => {
    console.error('Asynchronous error caught.', err);
});

Debugging a sandboxed code

You can debug or inspect code running in the sandbox as if it was running in a normal process.

Example

/tmp/main.js:

const {VM, VMScript} = require('.');
const fs = require('fs');
const file = `${__dirname}/sandbox.js`;

// By providing a file name as second argument you enable breakpoints
const script = new VMScript(fs.readFileSync(file), file);

new VM().run(script);

/tmp/sandbox.js

const foo = 'ahoj';

// The debugger keyword works just fine everywhere.
// Even without specifying a file name to the VMScript object.
debugger;

Read-only objects (experimental)

To prevent sandboxed scripts from adding, changing, or deleting properties from the proxied objects, you can use freeze methods to make the object read-only. This is only effective inside VM. Frozen objects are affected deeply. Primitive types cannot be frozen.

Example without using freeze:

const util = {
    add: (a, b) => a + b
}

const vm = new VM({
    sandbox: {util}
});

vm.run('util.add = (a, b) => a - b');
console.log(util.add(1, 1)); // returns 0

Example with using freeze:

const vm = new VM(); // Objects specified in the sandbox cannot be frozen.
vm.freeze(util, 'util'); // Second argument adds object to global.

vm.run('util.add = (a, b) => a - b'); // Fails silently when not in strict mode.
console.log(util.add(1, 1)); // returns 2

IMPORTANT: It is not possible to freeze objects that have already been proxied to the VM.

Protected objects (experimental)

Unlike freeze, this method allows sandboxed scripts to add, change, or delete properties on objects, with one exception - it is not possible to attach functions. Sandboxed scripts are therefore not able to modify methods like toJSON, toString or inspect.

IMPORTANT: It is not possible to protect objects that have already been proxied to the VM.

Cross-sandbox relationships

const assert = require('assert');
const {VM} = require('vm2');

const sandbox = {
    object: new Object(),
    func: new Function(),
    buffer: new Buffer([0x01, 0x05])
}

const vm = new VM({sandbox});

assert.ok(vm.run(`object`) === sandbox.object);
assert.ok(vm.run(`object instanceof Object`));
assert.ok(vm.run(`object`) instanceof Object);
assert.ok(vm.run(`object.__proto__ === Object.prototype`));
assert.ok(vm.run(`object`).__proto__ === Object.prototype);

assert.ok(vm.run(`func`) === sandbox.func);
assert.ok(vm.run(`func instanceof Function`));
assert.ok(vm.run(`func`) instanceof Function);
assert.ok(vm.run(`func.__proto__ === Function.prototype`));
assert.ok(vm.run(`func`).__proto__ === Function.prototype);

assert.ok(vm.run(`new func() instanceof func`));
assert.ok(vm.run(`new func()`) instanceof sandbox.func);
assert.ok(vm.run(`new func().__proto__ === func.prototype`));
assert.ok(vm.run(`new func()`).__proto__ === sandbox.func.prototype);

assert.ok(vm.run(`buffer`) === sandbox.buffer);
assert.ok(vm.run(`buffer instanceof Buffer`));
assert.ok(vm.run(`buffer`) instanceof Buffer);
assert.ok(vm.run(`buffer.__proto__ === Buffer.prototype`));
assert.ok(vm.run(`buffer`).__proto__ === Buffer.prototype);
assert.ok(vm.run(`buffer.slice(0, 1) instanceof Buffer`));
assert.ok(vm.run(`buffer.slice(0, 1)`) instanceof Buffer);

CLI

Before you can use vm2 in the command line, install it globally with npm install vm2 -g.

vm2 ./script.js

Known Issues

Deployment

  1. Update the CHANGELOG.md
  2. Update the package.json version number
  3. Commit the changes
  4. Run npm publish

Sponsors

Integromat

</details>