(Delphi ActiveX) Decrypt S/MIME and Verify S/MIME Signatures

Delphi ActiveX example to decrypt S/MIME and verify S/MIME signatures. The S/MIME is unwrapped to get the original MIME prior to signing/encrypting.

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

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
mime: TChilkatMime;
success: Integer;
isEncrypted: Integer;
isSigned: Integer;
signerCert: IChilkatCert;
encryptCert: IChilkatCert;

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

mime := TChilkatMime.Create(Self);

// Load an S/MIME message from a file:
success := mime.LoadMimeFile('signedMime.txt');
if (success <> 1) then
  begin
    Memo1.Lines.Add(mime.LastErrorText);
    Exit;
  end;

// The ContainsEncryptedParts/ContainsSignedParts methods
// can be called to determine if the MIME is encrypted and/or signed:
isEncrypted := mime.ContainsEncryptedParts();
isSigned := mime.ContainsSignedParts();

// We don't want the "unwrap extras".  You'll see what those
// are in a few moments...
mime.UnwrapExtras := 0;

// To verify the signature, call UnwrapSecurity.  This will
// verify the signature(s) and decrypt the S/MIME and restore
// the MIME to the unsigned/unencrypted state.
// The results of what was found are present in the MIME object's
// properties, as well as extra header fields that are added
// to the unwrapped MIME.
success := mime.UnwrapSecurity();
if (success <> 1) then
  begin
    // UnwrapSecurity returns 1 if all signatures were
    // verified and all parts decrypted.
    Memo1.Lines.Add(mime.LastErrorText);
    Exit;
  end;

// The mime.UnwrapExtras property controls whether or not
// these additional fields are added to the unwrapped MIME:
// 
// X-NumPartsSigned: 1
// X-SignaturesValid: yes
// X-NumPartsEncrypted: 1
// X-Decrypted: no
// 
// The X-NumPartsSigned/X-SignaturesValid headers are added
// if the MIME was signed.  
// 
// The X-NumPartsEncrypted/X-Decrypted headers are added
// if the MIME was encrypted.
// 

// If the MIME was signed, get the certificate used for signing.
if (isSigned = 1) then
  begin
    // The NumSignerCerts property indicates how many certificates
    // were used for signing.  This example will assume the value is 1.
    // To get the 1st signer cert, call GetSignerCert with an index of 0:
    signerCert := mime.GetSignerCert(0);
    if (mime.LastMethodSuccess = 1) then
      begin
        Memo1.Lines.Add('**** Signer Cert: ' + signerCert.SubjectCN);

      end;
  end;

// If the MIME was encrypted, get the certificate used for encryption:
if (isEncrypted = 1) then
  begin
    // The NumEncryptCerts property indicates how many certificates
    // were used for encrypting.  This example will assume the value is 1.
    // To get the 1st encrypt cert, call GetEncryptCert with an index of 0:
    encryptCert := mime.GetEncryptCert(0);
    if (mime.LastMethodSuccess = 1) then
      begin
        Memo1.Lines.Add('**** Encrypt Cert: ' + encryptCert.SubjectCN);

      end;
  end;

// Display the unwrapped MIME:
Memo1.Lines.Add(mime.GetMime());

// Save the unwrapped MIME to a file:
success := mime.SaveMime('unwrappedMime.txt');
end;