Pascal (Lazarus/Delphi)

Create an Opaque (Attached) S/MIME Signature

Demonstrates the Chilkat Mime.ConvertToSigned method, which creates an opaque (attached) S/MIME signature. The only argument is the signing Cert. On success the entity is replaced by a CMS/PKCS #7 signed-data structure that wraps the content inside the 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.

Background: An opaque signature bundles the content inside the CMS structure, so the message is a single application/pkcs7-mime blob that only S/MIME-aware software can read. It is more tamper-resistant in transit — nothing can alter the content without breaking the wrapper — at the cost of the backward compatibility a detached signature offers. Use it when every recipient is known to support S/MIME.

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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 OPAQUE (attached) S/MIME signature.  The entity is replaced by a CMS/PKCS #7
  //  signed-data structure that wraps the content inside the signature.
  success := mime.ConvertToSigned(cert);
  if (success = False) then
    begin
      WriteLn(mime.LastErrorText);
      Exit;
    end;

  success := mime.SaveMime('qa_output/signed_opaque.eml');
  if (success = False) then
    begin
      WriteLn(mime.LastErrorText);
      Exit;
    end;
  WriteLn('Message converted to an opaque signed message.');


  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.