Dart

Verify JWT Using HS256, HS384, or HS512

See more JSON Web Token (JWT) Examples

Demonstrates how to verify a JWT that was signed using HS256, HS384, or HS512. (HS256 is JWT's acronym for HMAC-SHA256.)

This example verifies the signature. It also does the following:

• Checks to see if the time constraints ("nbf" and "exp") are valid.
• Recovers the original JOSE header.
• Recovers the original claims JSON.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // Demonstrates how to verify an HMAC JWT using a shared secret (password).

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

  final jwt = CkJwt();

  final token = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJodHRwOi8vZXhhbXBsZS5vcmciLCJzdWIiOiJKb2huIiwiYXVkIjoiaHR0cDovL2V4YW1wbGUuY29tIiwiaWF0IjoxNDYzNDMxODEyLCJuYmYiOjE0NjM0MzE4MTIsImV4cCI6MTQ2MzQzNTQxMn0.SHnMJ11qJH5pbp22YchT_9fL2HIx0koHiUHLG67_foU';

  // First verify the signature.
  // The password used to create this JWT was "secret".
  var sigVerified = true;
  try {
    jwt.verifyJwt(token, 'secret');
  } on ChilkatException {
    sigVerified = false;
  }
  print('with correct password: $sigVerified');

  // Now try with a different password:
  sigVerified = true;
  try {
    jwt.verifyJwt(token, 'secret2');
  } on ChilkatException {
    sigVerified = false;
  }
  print('with incorrect password $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());
}