Pascal (Lazarus/Delphi)

Add an S/MIME Detached Signature

Demonstrates the Chilkat Mime.AddDetachedSignature method, which creates an S/MIME detached signature. The only argument is the signing Cert, which must have access to its private key. On success the entity becomes a multipart/signed with the content and a separate signature part.

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 detached signature (multipart/signed) keeps the original content readable alongside a separate signature part — so recipients whose software does not understand S/MIME still see the message, they just cannot verify it. That backward compatibility makes detached the usual choice for signed email. The signer proves authorship with a certificate that carries its private key.

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Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Cert,
  Chilkat.Mime;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  mime: TMime;
  pfxPassword: string;
  cert: TCert;

begin
  success := False;

  mime := TMime.Create;
  success := mime.SetBodyFromPlainText('This message will be signed.');
  if (success = False) then
    begin
      WriteLn(mime.LastErrorText);
      Exit;
    end;
  //  Load the signing certificate (which must have access to its private key) from a PFX file.
  //  The PFX password should come from a secure source rather than being hard-coded.
  pfxPassword := 'myPfxPassword';
  cert := TCert.Create;
  success := cert.LoadPfxFile('qa_data/signer.pfx',pfxPassword);
  if (success = False) then
    begin
      WriteLn(cert.LastErrorText);
      Exit;
    end;

  //  Create an S/MIME detached signature.  The object becomes a multipart/signed entity with the
  //  original content and a separate signature part.
  success := mime.AddDetachedSignature(cert);
  if (success = False) then
    begin
      WriteLn(mime.LastErrorText);
      Exit;
    end;

  success := mime.SaveMime('qa_output/signed.eml');
  if (success = False) then
    begin
      WriteLn(mime.LastErrorText);
      Exit;
    end;
  WriteLn('Detached signature added.');


  mime.Free;
  cert.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.