(Delphi DLL) Verify Opaque Signature and Retrieve Signing Certificates

Demonstrates how to verify a PCKS7 opaque digital signature (signed data), extract the original file/data, and then extract the certificate(s) that were used to sign.

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, BinData, CertChain, Cert, Crypt2;

...

procedure TForm1.Button1Click(Sender: TObject);
var
crypt: HCkCrypt2;
success: Boolean;
binData: HCkBinData;
numCerts: Integer;
i: Integer;
cert: HCkCert;
certChain: HCkCertChain;

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

crypt := CkCrypt2_Create();

// Verify a PKCS7 signed-data (opaque signature) file and extract the original content to a file.
success := CkCrypt2_VerifyP7M(crypt,'qa_data/p7m/opaqueSig.p7','qa_output/originalData.dat');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkCrypt2__lastErrorText(crypt));
    Exit;
  end;

// Alternatively, we can do it in memory...
binData := CkBinData_Create();
success := CkBinData_LoadFile(binData,'qa_data/p7m/opaqueSig.p7');
// Your app should check for success, but we'll skip the check for brevity..

// If verified, the signature is unwrapped and binData is replaced with the original data that was signed.
success := CkCrypt2_OpaqueVerifyBd(crypt,binData);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkCrypt2__lastErrorText(crypt));
    Exit;
  end;

// For our testing, we signed some text, so we can get it from the binData..
Memo1.Lines.Add('Original Data:');
Memo1.Lines.Add(CkBinData__getString(binData,'utf-8'));

// After any method call that verifies a signature, the crypt object will contain the certificate(s)
// that were used for signing (assuming the X.509 certs were available in the signature, which is typically the case).

// Get the number of signing certificates, and get each..
numCerts := CkCrypt2_getNumSignerCerts(crypt);
i := 0;
while i < numCerts do
  begin
    cert := CkCrypt2_GetSignerCert(crypt,i);
    Memo1.Lines.Add(CkCert__subjectDN(cert));
    CkCert_Dispose(cert);
    i := i + 1;
  end;

// We could also get the complete certificate chain of each signer cert,
// assuming the certs in the chain of authentication to the trusted root
// are available on the system, or provided to Chilkat by some other means
// (such as via the XmlCertVault class, the TrustedRoots class, etc.)
i := 0;
while i < numCerts do
  begin
    certChain := CkCrypt2_GetSignerCertChain(crypt,i);
    // You can examine the various properties and methods for certChain in the online
    // reference documentation...
    CkCertChain_Dispose(certChain);
    i := i + 1;
  end;

CkCrypt2_Dispose(crypt);
CkBinData_Dispose(binData);

end;