Dart Requires Chilkat v11.0.0+

Validate JWS Using RSASSA-PKCS1-v1_5 SHA-256

See more JSON Web Signatures (JWS) Examples

Validates a JSON Web Signature (JWS) that uses RSASSA-PKCS1-v1_5 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 an RSA public key to validate and recover the protected header and payload.

  // We only need a public key for signature validation.  This is the RSA public key
  // that is used:

  //      {"kty":"RSA", 
  //       "n":"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx
  //            HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs
  //            D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH
  //            SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV
  //            MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8
  //            NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ", 
  //       "e":"AQAB"
  //      }

  final sbPubKey = CkStringBuilder();
  sbPubKey.append('{"kty":"RSA",');
  sbPubKey.append('"n":"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx');
  sbPubKey.append('HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs');
  sbPubKey.append('D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH');
  sbPubKey.append('SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV');
  sbPubKey.append('MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8');
  sbPubKey.append('NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ",');
  sbPubKey.append('"e":"AQAB"');
  sbPubKey.append('}');

  final pubKey = CkPublicKey();
  try {
    pubKey.loadFromString(sbPubKey.getAsString());
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final jws = CkJws();

  // Set the RSA public key:
  final signatureIndex = 0;
  jws.setPublicKey(signatureIndex, pubKey);

  // Load the JWS.
  final sbJws = CkStringBuilder();
  sbJws.append('eyJhbGciOiJSUzI1NiJ9');
  sbJws.append('.');
  sbJws.append('eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt');
  sbJws.append('cGxlLmNvbS9pc19yb290Ijp0cnVlfQ');
  sbJws.append('.');
  sbJws.append('cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7');
  sbJws.append('AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4');
  sbJws.append('BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K');
  sbJws.append('0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqv');
  sbJws.append('hJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrB');
  sbJws.append('p0igcN_IoypGlUPQGe77Rw');

  try {
    jws.loadJwsSb(sbJws);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // 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 RSA key was incorrect, the JWS was invalid, or both.');
    return;
  }

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

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

  // 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:
  // 	{ 
  // 	  "alg": "RS256"
  // 	}
}