AuthenticatorResponse.clientDataJSON

The clientDataJSON object is an ArrayBuffer containing a JSON String of the various browser data that was used for the WebAuthn create() or get() call. It is included in both an AuthenticatorAttestationResponse and an AuthenticatorAssertionResponse within a PublicKeyCredential. The reason for storing the data as a ArrayBuffer rather than a String or an actual JavaScript object is that the object is effectively signed over by the authenticator, and if the order of the properties of the JavaScript object were not preserved then the signature verification would fail.

Syntax

TBD

Properties

After the clientDataJSON is converted from an ArrayBuffer to a JavaScript object, it will have the following properties:

clientDataJSON.type

TBD

clientDataJSON.challenge

TBD

clientDataJSON.origin

TBD

clientDataJSON.tokenBindingId Optional

TBD

clientDataJSON.clientExtensions Optional

TBD

clientDataJSON.authenticatorExtensions Optional

TBD

Examples

function arrayBufferToStr(buf) {
    return String.fromCharCode.apply(null, new Uint8Array(buf));
}

// pk is a PublicKeyCredential that is the result of a create() or get() Promise
var clientDataStr = arrayBufferToStr(pk.clientDataJSON);
var clientDataObj = JSON.parse(clientDataStr);

console.log (clientDataObj.type); // "webauthn.create" or "webauthn.get"
console.log (clientDataObj.challenge); // base64 encoded String containing the original challenge
console.log (clientDataObj.origin); // the window.origin

Specifications

Browser compatibilityUpdate compatibility data on GitHub