Dart Requires Chilkat v11.0.0+

Validate JWS Using HMAC SHA-256

See more JSON Web Signatures (JWS) Examples

Validates a JSON Web Signature (JWS) using HMAC SHA-256. Dart

import 'package:chilkat/chilkat.dart';

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

  // This example takes a JSON signature in compact serialization format,
  // and uses a MAC key to validate and recover the protected header and payload.

  final jws = CkJws();

  // Set the HMAC key:
  final hmacKey = 'AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow';
  final signatureIndex = 0;
  jws.setMacKey(signatureIndex, hmacKey, 'base64url');

  // Load the JWS.
  final jwsCompact = 'eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ.dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk';
  jws.loadJws(jwsCompact);

  // Validate the 1st (and only) signature at index 0..
  final v = jws.validate(signatureIndex);
  if (v < 0) {
    // Perhaps Chilkat was not unlocked or the trial expired..
    print('Method call failed for some other reason.');
    print(jws.lastErrorText);
    return;
  }

  if (v == 0) {
    print('Invalid signature.  The MAC key was incorrect, the JWS was invalid, or both.');
    return;
  }

  // If we get here, the signature was validated..
  print('Signature validated.');

  // Recover the original content:
  print('Recovered content:');
  print(jws.getPayload('utf-8'));

  // Examine the protected header:

  final joseHeader = CkJsonObject();
  try {
    jws.getProtectedH(signatureIndex, joseHeader);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  joseHeader.emitCompact = false;

  print('Protected (JOSE) header:');
  print(joseHeader.emit());

  // Output:

  // 	Signature validated.
  // 	Recovered content:
  // 	{"iss":"joe",
  // 	 "exp":1300819380,
  // 	 "http://example.com/is_root":true}
  // 	Protected (JOSE) header:
  // 	{ 
  // 	  "typ": "JWT",
  // 	  "alg": "HS256"
  // 	}
}