@github/webauthn-json

webauthn-json is a client-side Javascript library that serves as convenience wrapper for the the WebAuthn API by encoding binary data using base64url (also known as "websafe" or "urlsafe" base64).

The WebAuthn API itself takes input and output values that look almost like JSON, except that binary data is represented as ArrayBuffers. Using webauthn-json allows the data to be sent from/to the server as normal JSON without client-side processing.

Usage

1. Replace calls to navigator.credentials.create() with create(), and navigator.credentials.get() with get().
2. Encode/decode binary values on the server as base64url.

Example

Install using:

npm install --save @github/webauthn-json

Then:

import {create} from "@github/webauthn-json"

async auth() {
  const request = await fetch("...");
  const response = create(request.json());
  await fetch("...", {
    method: "POST",
    body: JSON.stringify(response)
  });
}

See here for fully working client-side demo code.

API

function create(requestJSON: JSON): Promise<JSON>;
function get(requestJSON: JSON): Promise<JSON>;
function supported(): boolean;

Schema

There are are several ways to encode JSON with binary fields. webauthn-json focuses on one simple approach: converting the known structure using a simple (custom) schema format. webauthn-json uses a few tricks for a compact schema encoding: the production build is about ≈2KB uncompressed (<1KB gzipped).

Right now, we only convert fields explicitly known to be used by the WebAuthn API. This means that you'll have to update to a newer version of this library if you want to use new fields in the future.

To print the current schema, run:

npx @github/webauthn-json schema

Extensions

Modern browsers generally only support a single extension: the appid string. If you need to convert additional input or output extensions, use createExtended() and getExtended() from @github/webauthn-json/extended.

Contributions

The scope of webauthn-json is fairly small — it's essentially feature-complete. However, we're happy to accept issues or pull requests that address the core goal of the project!