Create a `verifier` and `challenge` in Expo (React Native) for the Authorization Code Grant Flow with PKCE (Auth0)

expo-pkce.js

// Usage:
// const [verifier, challenge] = await createVerifierChallenge();

import * as Random from 'expo-random';
import * as Crypto from 'expo-crypto';

if (typeof Buffer === 'undefined') {
  global.Buffer = require('buffer').Buffer;
}

function base64URLEncode(str) {
  return str
    .toString('base64')
    .replace(/\+/g, '-')
    .replace(/\//g, '_')
    .replace(/=/g, '');
}

export const createVerifierChallenge = () => {
  return new Promise(async (resolve, reject) => {
    const randomBytes = await Random.getRandomBytesAsync(32);
    const verifier = base64URLEncode(Buffer.from(randomBytes));

    const challengeBase64 = await Crypto.digestStringAsync(
      Crypto.CryptoDigestAlgorithm.SHA256,
      verifier,
      { encoding: Crypto.CryptoEncoding.BASE64 }
    );
    const challenge = challengeBase64
      .replace(/\+/g, '-')
      .replace(/\//g, '_')
      .replace(/=/g, '');

    resolve([verifier, challenge]);
  });
};

Hi, does this work with react-native init projects?

Hi, does this work with react-native init projects?

@1kvnlee It should also work for regular RN projects, but you would need to change the Random and Crypto dependencies from Expo to e.g. https://github.com/tradle/react-native-crypto

@fabe Thank you

Nice, thanks