(Delphi DLL) Add DKIM-Signature Header to MIME / Email

Demonstrates how to add a DKIM-Signature header field to a MIME message.

Note: The DKIM / DomainKey functionality is included with the Chilkat MIME license.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, PrivateKey, CkByteData, Dkim;

...

procedure TForm1.Button1Click(Sender: TObject);
var
dkim: HCkDkim;
password: PWideChar;
privKey: HCkPrivateKey;
success: Boolean;
mimeData: HCkByteData;
dkimSignedMime: HCkByteData;

begin
// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

dkim := CkDkim_Create();

// To create a DKIM signature for email (i.e. MIME),
// you'll need to provide the following:
// (1) An RSA private key in any common file format.
// (2) The domain name (typically the same domain
// as the sender of an email).
// (3) A selector for the domain name -- an arbitrary string
// to identify the matching public key in DNS.

// To allow an email recipient to verify the DKIM signature via an
// external email client supporting DKIM or using other software,
// you will need to create a DNS record with the selector
// and matching public key.  This example does not provide
// information about DKIM DNS record creation.  
// (Chilkat does not provide an API for creating DNS records.  
// Creating the DKIM DNS record is something you would do
// manually.)

// Set the domain and selector:
// You'll need to provide your own values here..
CkDkim_putDkimDomain(dkim,'chilkatsoft.com');
CkDkim_putDkimSelector(dkim,'tuna');

// Load a private key from any common RSA private key
// format, such as DER, PKCS8, PEM, XML, etc.
// The LoadDkimPkFile method automatically detects
// the file format and reads it appropriately.
// If a password is not required, you'll still need to provide
// a password string argument, but it is ignored.

password := 'optionalPassword';
privKey := CkPrivateKey_Create();
success := CkPrivateKey_LoadAnyFormatFile(privKey,'myPrivateKey.pem',password);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkPrivateKey__lastErrorText(privKey));
    Exit;
  end;

success := CkDkim_SetDkimPrivateKey(dkim,privKey);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkDkim__lastErrorText(dkim));
    Exit;
  end;

// Load a MIME file.
mimeData := CkByteData_Create();
success := CkByteData_loadFile(mimeData,'testMessage.eml');
if (success <> True) then
  begin
    Memo1.Lines.Add('Failed to load file.');
    Exit;
  end;

// Sign it.  This adds the DKIM-Signature header and
// returns the new MIME with DKIM-Signature added.
dkimSignedMime := CkByteData_Create();
success := CkDkim_AddDkimSignature(dkim,mimeData,dkimSignedMime);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkDkim__lastErrorText(dkim));
    Exit;
  end;

success := CkByteData_saveFile(dkimSignedMime,'dkimSigned.eml');
if (success <> True) then
  begin
    Memo1.Lines.Add('Failed to save file.');
    Exit;
  end;

Memo1.Lines.Add('Success.');

CkDkim_Dispose(dkim);
CkPrivateKey_Dispose(privKey);
CkByteData_Dispose(mimeData);
CkByteData_Dispose(dkimSignedMime);

end;