Android™

Get the S/MIME Signer's Certificate

Demonstrates the Chilkat Mime.LastSignerCert method, which loads the signer certificate at a zero-based index from the most recent successful verification (or security-unwrapping) into a Cert. The first argument is the signer index and the second is the receiving Cert.

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: Verifying tells you the signature is mathematically valid, but you usually also need to know who signed — the subject, the issuer, the validity dates — to decide whether to trust it. This retrieves each signer's certificate after verification so your code can inspect and apply its own trust rules. A message can have multiple signers, so iterate from 0 to NumSignerCerts - 1.

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// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    boolean success = false;

    CkMime mime = new CkMime();
    success = mime.LoadMimeFile("qa_data/signed.eml");
    if (success == false) {
        Log.i(TAG, mime.lastErrorText());
        return;
        }

    //  After a successful verification, load each signer's certificate to inspect it.  The 1st argument
    //  is the zero-based signer index and the 2nd is a Cert object that receives the certificate.
    success = mime.Verify();
    if (success != true) {
        Log.i(TAG, mime.lastErrorText());
        return;
        }

    int n = mime.get_NumSignerCerts();
    CkCert cert = new CkCert();
    int i;
    for (i = 0; i <= n - 1; i++) {
        success = mime.LastSignerCert(i,cert);
        if (success == false) {
            Log.i(TAG, mime.lastErrorText());
            return;
            }

        Log.i(TAG, "Signer " + String.valueOf(i) + ": " + cert.subjectCN() + " (issued by " + cert.issuerCN() + ")");
        }


  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}