Dart

Check for an S/MIME Signing Time

Demonstrates the Chilkat Mime.HasSignatureSigningTime method, which returns whether the signer at a zero-based index included a CMS signingTime signed attribute. The only argument is the signer index; use NumSignerCerts for the count.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: A signing time records when the signer claims to have signed, which matters for auditing and for validating a certificate that has since expired. It is an optional signed attribute, so not every signature has one — this predicate lets you check before calling GetSignatureSigningTimeStr, avoiding an error for signers that omitted it. Being a signed attribute, it is covered by the signature and cannot be altered undetected.

Chilkat Dart Downloads

Download Chilkat for Dart

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  final mime = CkMime();
  try {
    mime.loadMimeFile('qa_data/signed.eml');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // After verifying, check whether each signer included a CMS signingTime signed attribute.  The
  // only argument is the zero-based signer index.
  try {
    mime.verify();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final n = mime.numSignerCerts;
  for (var i = 0; i < n; i++) {
    if (mime.hasSignatureSigningTime(i)) {
      print('Signer $i included a signing time.');
    } else {
      print('Signer $i did not include a signing time.');
    }
  }
}