Dart

Get an S/MIME Signing Time

Demonstrates the Chilkat Mime.GetSignatureSigningTimeStr method, which returns the CMS signingTime attribute for the signer at a zero-based index, as an RFC 822-style date string in GMT. The only argument is the signer index.

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: This is the timestamp the signer asserted at signing — useful for "when was this signed" audit trails and for evaluating whether the signing certificate was valid at that moment. Because it is a signed attribute, it is tamper-evident. Guard the call with HasSignatureSigningTime, since the attribute is optional. Note it is the signer's claim, not a trusted third-party timestamp.

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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, get the CMS signingTime for each signer that has one, as an RFC 822 date string
  // in GMT.  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++) {
    // Only signers that included a signing time have one to retrieve.
    if (mime.hasSignatureSigningTime(i)) {
      final String signingTime;
      try {
        signingTime = mime.getSignatureSigningTimeStr(i);
      } on ChilkatException catch (e) {
        print(e.lastErrorText);
        return;
      }

      print('Signer $i signing time: $signingTime');
    }
  }
}