WebAuthnStorage

Deterministic storage using WebAuthn

npm i @hazae41/webauthnstorage

**Node Package **

About

Use WebAuthn as a authentication-protected storage of arbitrary bytes

This WON'T use any cryptoprocessor (HSM, Secure Enclave) as it stores the bytes in userHandle (probably on disk)

This is only used to prevent unauthenticated access to the stored values

Supply-chain attacks, phishing, misclick, phone-left-on-the-table attack would still require user authentication before accessing the data

Features

Current features

• 100% TypeScript and ESM
• No external dependencies
• Battle-tested on many browsers

Usage

import { WebAuthnStorage } from "@hazae41/webauthnstorage"

async function create() {
  /**
   * Generate a new private key
   */
  const bytes = crypto.getRandomValues(new Uint8Array(32))

  /**
   * Store the private key into authenticated storage
   */
  const handle = await WebAuthnStorage.create("My Private Key", bytes)
  
  /**
   * Store the handle to the private key into some unauthenticated storage
   */
  const cache = await caches.open("my-storage")
  const request = new Request("my-private-key")
  const response = new Response(handle)
  await cache.put(request, response)
}

async function get() {
  /**
   * Retrieve the handle to the private key from some unauthenticated storage
   */
  const cache = await caches.open("my-storage")
  const request = new Request("my-private-key")
  const response = await cache.match(request)
  const handle = new Uint8Array(await response.arrayBuffer())

  /**
   * Retrieve the private key from authenticated storage
   */
  const bytes = await WebAuthnStorage.get(handle)
}

Limitations

Storage size

Values must have a maximum length of 64 bytes

https://github.com/w3c/webauthn/issues/1302

I recommend only storing private keys, signatures, and identifiers

User interation

This requires user interaction on most browsers

e.g. You have to create and get when the user clicks a button

const [handle, setHandle] = useState<Uint8Array>()

const onCreateClick = useCallback(async () => {
  const bytes = crypto.getRandomValues(new Uint8Array(32))
  const handle = await WebAuthnStorage.create("My Private Key", bytes)

  setHandle(handle)
}, [])

const onGetClick = useCallback(async () => {
  const bytes = await WebAuthnStorage.get(handle)

  console.log(bytes)
}, [handle])

return <>
  <button onClick={onCreateClick}>
    Create
  </button>
  <button onClick={onGetClick}>
    Get
  </button>
</>