v4.3.0

Packages:

• @simplewebauthn/[email protected]

Changes:

• [server] The expectedChallenge argument passed to verifyRegistrationResponse() can now be a function that accepts a Base64URL string and returns a boolean to run custom logic against the clientDataJSON.challenge returned by the authenticator. This allows for arbitrary data to be included in the challenge so it can be signed by the authenticator.

After generating registration options, the challenge can be augmented with additional data:

const options = generateRegistrationOptions(opts);

// Remember the plain challenge
inMemoryUserDeviceDB[loggedInUserId].currentChallenge = options.challenge;

// Add data to be signed
options.challenge = base64url(JSON.stringify({
  actualChallenge: options.challenge,
  arbitraryData: 'arbitraryDataForSigning',
}));

Then, when invoking verifyRegistrationResponse(), pass in a method for expectedChallenge to parse the challenge and return a boolean:

const expectedChallenge = inMemoryUserDeviceDB[loggedInUserId].currentChallenge;

const verification = await verifyRegistrationResponse({
  expectedChallenge: (challenge: string) => {
    const parsedChallenge = JSON.parse(base64url.decode(challenge));
    return parsedChallenge.actualChallenge === expectedChallenge;
  },
  // ...
});

To retrieve the arbitrary data afterwards, use decodeClientDataJSON() afterwards to get it out:

import { decodeClientDataJSON } from '@simplewebauthn/server/helpers';

const { challenge } = decodeClientDataJSON(response.clientDataJSON);
const parsedChallenge = JSON.parse(base64url.decode(challenge));
console.log(parsedChallenge.arbitraryData); // 'arbitraryDataForSigning'