Isolated-function NPM

Install

npm install isolated-function --save

Quickstart

isolated-function is a modern solution for running untrusted code in Node.js.

const isolatedFunction = require('isolated-function')

/* create an isolated-function, with resources limitation */
const [sum, teardown] = isolatedFunction((y, z) => y + z, {
  memory: 128, // in MB
  timeout: 10000 // in milliseconds
})

/* interact with the isolated-function */
const { value, profiling } = await sum(3, 2)

/* close resources associated with the isolated-function initialization */
await teardown()

Minimal privilege execution

The hosted code runs in a separate process, with minimal privilege, using Node.js permission model API.

const [fn, teardown] = isolatedFunction(() => {
  const fs = require('fs')
  fs.writeFileSync('/etc/passwd', 'foo')
})

await fn()
// => PermissionError: Access to 'FileSystemWrite' has been restricted.

If you exceed your limit, an error will occur. Any of the following interaction will throw an error:

Native modules
Child process
Worker Threads
Inspector protocol
File system access
WASI

Auto install dependencies

The hosted code is parsed for detecting require/import calls and install these dependencies:

const [isEmoji, teardown] = isolatedFunction(input => {
  /* this dependency only exists inside the isolated function */
  const isEmoji = require('is-standard-emoji@1.0.0') // default is latest
  return isEmoji(input)
})

await isEmoji('🙌') // => true
await isEmoji('foo') // => false
await teardown()

The dependencies, along with the hosted code, are bundled by esbuild into a single file that will be evaluated at runtime.

Execution profiling

Any hosted code execution will be run in their own separate process:

/** make a function to consume ~128MB */
const [fn, teardown] = isolatedFunction(() => {
  const storage = []
  const oneMegabyte = 1024 * 1024
  while (storage.length < 78) {
    const array = new Uint8Array(oneMegabyte)
    for (let ii = 0; ii < oneMegabyte; ii += 4096) {
      array[ii] = 1
    }
    storage.push(array)
  }
})
t.teardown(cleanup)

const { value, profiling } = await fn()
console.log(profiling)
// {
//   memory: 128204800,
//   duration: 54.98325
// }

Each execution has a profiling, which helps understand what happened.

Resource limits

You can limit a isolated-function by memory:

const [fn, teardown] = isolatedFunction(() => {
  const storage = []
  const oneMegabyte = 1024 * 1024
  while (storage.length < 78) {
    const array = new Uint8Array(oneMegabyte)
    for (let ii = 0; ii < oneMegabyte; ii += 4096) {
      array[ii] = 1
    }
    storage.push(array)
  }
}, { memory: 64 })

await fn()
// =>  MemoryError: Out of memory

or by execution duration:

const [fn, teardown] = isolatedFunction(() => {
  const delay = ms => new Promise(resolve => setTimeout(resolve, ms))
  await delay(duration)
  return 'done'
}, { timeout: 50 })

await fn(100)
// =>  TimeoutError: Execution timed out

Logging

The logs are collected into a logging object returned after the execution:

const [fn, teardown] = isolatedFunction(() => {
  console.log('console.log')
  console.info('console.info')
  console.debug('console.debug')
  console.warn('console.warn')
  console.error('console.error')
  return 'done'
})

const { logging } await fn()

console.log(logging)
// {
//   log: ['console.log'],
//   info: ['console.info'],
//   debug: ['console.debug'],
//   warn: ['console.warn'],
//   error: ['console.error']
// }

Error handling

Any error during isolated-function execution will be propagated:

const [fn, cleanup] = isolatedFunction(() => {
  throw new TypeError('oh no!')
})

const result = await fn()
// TypeError: oh no!

You can also return the error instead of throwing it with { throwError: false }:

const [fn, cleanup] = isolatedFunction(() => {
  throw new TypeError('oh no!')
})

const { isFullfiled, value } = await fn()

if (!isFufilled) {
  console.error(value)
  // TypeError: oh no!
}

API

isolatedFunction(code, options)

code

Required Type: function

The hosted function to run.

options

memory

Type: number Default: Infinity

Set the function memory limit, in megabytes.

throwError

Type: boolean Default: false

When is true, it returns the error rather than throw it.

The error will be accessible against { value: error, isFufilled: false } object.

Set the function memory limit, in megabytes.

timeout

Type: number Default: Infinity

Timeout after a specified amount of time, in milliseconds.

tmpdir

Type: function

It setup the temporal folder to be used for installing code dependencies.

The default implementation is:

const tmpdir = async () => {
  const cwd = await fs.mkdtemp(path.join(require('os').tmpdir(), 'compile-'))
  await fs.mkdir(cwd, { recursive: true })
  const cleanup = () => fs.rm(cwd, { recursive: true, force: true })
  return { cwd, cleanup }
}