Verifies ALB token from Cognito

VerifyCognitoALBToken.js

// Get OIDC JWT from headers
const encodeJwt = req.headers["x-amzn-oidc-data"];
const jwtHeaders = encodeJwt.split(".")[0];
const decodedJwtHeaders = Buffer.from(jwtHeaders, "base64");
const decodedJson = JSON.parse(decodedJwtHeaders);
const kid = decodedJson["kid"];

// Lookup ALB public key for JWT
const region = "us-east-1";
const url = `https://public-keys.auth.elb.${region}.amazonaws.com/${kid}`;
request(url, (error, response, body) => {
  jwt.verify(encodeJwt, body, {algorithms: ["ES256"]}, (err, decoded) => {
    // We should have a valid token, except for https://github.com/brianloveswords/node-jws/pull/84
  });
});