safe-eval

NOTE

safe-eval 0.3.0 and below are affected by a sandbox breakout vulnerability - NSP 337, CVE-2017-16088.

Version 0.4.0 fixes this vulnerability. It is highly recommended to upgrade to the latest version if you are using safe-eval for executing code not generated by yourself. Thanks @kauegimenes for the patch.

UPDATE 27/08/2018: There are still ways to crash the Node process, please use safe-eval only with content created by yourself or from trusted sources. User-submitted data should not be run through safe-eval. Thanks @cpcallen for the report.

What is this?

safe-eval lets you execute JavaScript code without having to use the much discouraged and feared upon eval(). safe-eval has access to all the standard APIs of the V8 JavaScript Engine. By default, it does not have access to the Node.js API, but can be given access using a context object. It is implemented using node's vm module.

Currently, it works only with Node.js, and the JavaScript code must be an expression (something which evaluates to a value).

Installation

npm install safe-eval --save

Usage

var safeEval = require('safe-eval')

safeEval(code, [context], [options])

code is the JavaScript code you want to execute.

context is an object of methods and properties, these methods and properties are interpreted as global objects in code. Be careful about the objects you are passing to the context API, because they can completely defeat the purpose of safe-eval.

options is the options object for the vm executing the code.

Examples

// string concatenation
var code = '"app" + "le"'
var evaluated = safeEval(code) // "apple"

// math
var code = 'Math.floor(22/7)'
var evaluated = safeEval(code) // 3.142857142857143

// JSON
var code = '{name: "Borat", hobbies: ["disco dance", "sunbathing"]}'
var evaluated = safeEval(code) // {name: "Borat", hobbies: ["disco dance", "sunbathing"]}

// function expression
var code = '(function square(b) { return b * b; })(5)'
var evaluated = safeEval(code) // 25

// no access to Node.js objects
var code = 'process'
safeEval(code) // THROWS!

// your own context API - access to Node's process object and a custom function
var code = '{pid: process.pid, apple: a()}'
var context = {
  process: process,
  a: function () { return 'APPLE' }
}
var evaluated = safeEval(code, context) // { pid: 16987, apple: 'APPLE' }

// pass an options object to the vm
var code = 'process'
safeEval(code, {}, { filename: 'myfile.js'}) // myfile.js can be seen in the stacktrace

License (MIT)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.