Getting idToken having an accessToken

[Kostanos]

Hey, thank you for this library, it is very useful for Cloudflare Workers.

Question, is there a way to get the idToken having user's accessToken?

What I'm trying to accomplish, is to validate the authenticated user's request with Firebase to get user's information and authorize an action.

[koistya]

@Kostanos if you're using Firebase Auth on the client, most likely you want to authenticate the user with a Cloudflare Worker script using ID Token (docs):

On the client

import { getAuth } from "firebase/auth";

const auth = getAuth();
const req = new Request("/api/ping", { method: "POST" });
req.headers.set("Content-Type": "application/json");

if (auth.currentUser) {
  const idToken = await auth.currentUser.getIdToken();
  req.headers.set("Authorization", `Bearer ${idToken}`);
}

const res = await fetch(req);
const data = await res.json();

Cloudflare Worker script

import { Hono } from "hono";
import { verifyIdToken } from "web-auth-library/google";

const app = new Hono();

app.use(({ env, executionCtx, json }) => {
  const idToken = req.headers.get("authorization")?.match(/^Bearer (\S+)/)?.[1];
  
  if (idToken) {
    const token = await verifyIdToken({
      idToken: "...",
      waitUntil: executionCtx.waitUntil,
      env,
    });
    // => { sub: "xxx", email: "[email protected]", ... }
  }

  return json({ ... });
})

Where verifyIdToken({ idToken, ... }) returns a verified and decoded ID token containing user information (user ID, email, custom claims, etc.).