Dart Requires Chilkat v11.0.0+

Verify a JWT Created by the Amazon Cognito Service

See more JSON Web Token (JWT) Examples

Demonstrates how to verify a JWT created by the Amazon Cognito Service. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  // The public keys for this example are at https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json
  // Let's get them:

  final http = CkHttp();
  final sbJsonKeys = CkStringBuilder();
  try {
    http.quickGetSb('https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json', sbJsonKeys);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final jsonKeys = CkJsonObject();
  jsonKeys.loadSb(sbJsonKeys);
  jsonKeys.emitCompact = false;
  print(jsonKeys.emit());

  // Here are the keys:

  // {
  //   "keys": [
  //     {
  //       "alg": "RS256",
  //       "e": "AQAB",
  //       "kid": "1A/L5Fsb2EsEwxy5E0cmCMS1BnMe6Jl6NXiMig4iNwU=",
  //       "kty": "RSA",
  //       "n": "y0w7BJrIJYi ... jKG27z2P3OKw",
  //       "use": "sig"
  //     },
  //     {
  //       "alg": "RS256",
  //       "e": "AQAB",
  //       "kid": "mos6VTJnvDwurY3ghJg6IAPUq+dMwl6CL/iThzJOkzg=",
  //       "kty": "RSA",
  //       "n": "qbIEH-7tg6yrT ... 3Fj94ooTd0w",
  //       "use": "sig"
  //     }
  //   ]
  // }

  // Try the 1st key.
  final jsonKey1 = CkJsonObject();
  jsonKeys.objectOf2('keys[0]', jsonKey1);

  final pubKey1 = CkPublicKey();
  try {
    pubKey1.loadFromString(jsonKey1.emit());
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Success');

  final jwt = CkJwt();

  // I did not include the an actual AWS Cognito token here because our test sample used customer-provided data..
  final token = 'eyJ..asXg';

  // First verify the signature.
  var sigVerified = true;
  try {
    jwt.verifyJwtPk(token, pubKey1);
  } on ChilkatException {
    sigVerified = false;
  }
  print('verified: $sigVerified');

  // Let's see if the time constraints, if any, are valid.
  // The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
  // If the current system time is before the "nbf" time, or after the "exp" time,
  // then IsTimeValid will return false/0.
  // Also, we'll allow a leeway of 60 seconds to account for any clock skew.
  // Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
  final leeway = 60;
  final bTimeValid = jwt.isTimeValid(token, leeway);
  print('time constraints valid: $bTimeValid');

  // Now let's recover the original claims JSON (the payload).
  final payload = jwt.getPayload(token);
  // The payload will likely be in compact form:
  print(payload);

  // We can format for human viewing by loading it into Chilkat's JSON object
  // and emit.
  final json = CkJsonObject();
  json.load(payload);
  json.emitCompact = false;
  print(json.emit());

  // We can recover the original JOSE header in the same way:
  final joseHeader = jwt.getHeader(token);
  // The payload will likely be in compact form:
  print(joseHeader);

  // We can format for human viewing by loading it into Chilkat's JSON object
  // and emit.
  json.load(joseHeader);
  json.emitCompact = false;
  print(json.emit());
}