Create a DKIM-Signature for a MIME Message

See more DKIM / DomainKey Examples

Demonstrates the Chilkat Dkim.DkimSign method, which creates a DKIM-Signature header and prepends it to a complete MIME message held in a BinData, modifying it in place. The DkimAlg, DkimCanon, DkimDomain, DkimSelector, DkimHeaders, and DkimBodyLengthCount properties configure the generated signature.

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.

// 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;

    //  Demonstrates the Dkim.DkimSign method, which creates a DKIM-Signature header and prepends it to
    //  a complete MIME message.  The only argument is a BinData holding the MIME, which is modified in
    //  place.
    //  
    //  The DkimAlg, DkimCanon, DkimDomain, DkimSelector, DkimHeaders, and DkimBodyLengthCount
    //  properties configure the signature that is generated.

    CkDkim dkim = new CkDkim();

    //  Configure the DKIM signature.
    dkim.put_DkimDomain("example.com");
    dkim.put_DkimSelector("myselector");

    //  Signing algorithm written to the a= tag.
    dkim.put_DkimAlg("rsa-sha256");

    //  Canonicalization for headers and body, written to the c= tag.
    dkim.put_DkimCanon("relaxed/relaxed");

    //  Colon-separated list of header fields to sign, written to the h= tag.
    dkim.put_DkimHeaders("From:To:Subject:Date:Message-ID");

    //  Maximum number of canonicalized body bytes to hash.  0 means the entire body.
    dkim.put_DkimBodyLengthCount(0);

    //  Load the RSA private key and give it to the Dkim object.
    CkPrivateKey privKey = new CkPrivateKey();
    success = privKey.LoadPemFile("qa_data/dkim_private.pem");
    if (success == false) {
        Log.i(TAG, privKey.lastErrorText());
        return;
        }

    success = dkim.SetDkimPrivateKey(privKey);
    if (success == false) {
        Log.i(TAG, dkim.lastErrorText());
        return;
        }

    //  Load the complete MIME message to be signed.  It must already contain all headers, transfer
    //  encodings, MIME boundaries, and body bytes.
    CkBinData mimeData = new CkBinData();
    success = mimeData.LoadFile("qa_data/message.eml");
    if (success == false) {
        Log.i(TAG, mimeData.lastErrorText());
        return;
        }

    //  Sign.  The DKIM-Signature header is prepended to the MIME in place.
    success = dkim.DkimSign(mimeData);
    if (success == false) {
        Log.i(TAG, dkim.lastErrorText());
        return;
        }

    //  Save the signed message.
    success = mimeData.WriteFile("qa_output/signed.eml");
    if (success == false) {
        Log.i(TAG, mimeData.lastErrorText());
        return;
        }

    Log.i(TAG, "Message signed.");

  }

  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."
  }
}