(Delphi ActiveX) Extract PKCS7 Signature Digest

Demonstrates how to extract a signature digest from a PKCS7 signature.

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
crypt: TChilkatCrypt2;
p7mFile: WideString;
outPath: WideString;
verified: Integer;
pkcs7Data: TChilkatBinData;
sbBase64: TChilkatStringBuilder;
hexStr: WideString;
bHaveBase64: Integer;
i: Integer;
digest: WideString;

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

crypt := TChilkatCrypt2.Create(Self);

p7mFile := 'qa_data/p7m/test.pdf.p7m';
outPath := 'qa_output/test.pdf';

// First let's see if this .p7m signature can be verified, and the original file extracted.
verified := crypt.VerifyP7M(p7mFile,outPath);
if (verified <> 1) then
  begin
    Memo1.Lines.Add(crypt.LastErrorText);
    Exit;
  end;

// How many signers?
// (The NumSignerCerts property is set whenever a signature is verified.)
Memo1.Lines.Add('Num Signers: ' + IntToStr(crypt.NumSignerCerts));

// Load the .p7m into memory...
pkcs7Data := TChilkatBinData.Create(Self);
pkcs7Data.LoadFile(p7mFile);

// Check to see if this .p7m contains the binary bytes, or if it's
// already base64 encoded.  Get the 1st two bytes.  If the first two 
// bytes are the us-ascii values "MI", then we have base64.
sbBase64 := TChilkatStringBuilder.Create(Self);
hexStr := pkcs7Data.GetEncodedChunk(0,2,'hex');
sbBase64.Append(hexStr);

bHaveBase64 := 0;
if (sbBase64.ContentsEqual('4D49',1) = 1) then
  begin
    bHaveBase64 := 1;
    sbBase64.Clear();
    sbBase64.AppendBd(pkcs7Data.ControlInterface,'utf-8',0,0);
  end;

// Get each signer's signature digest.
crypt.EncodingMode := 'base64';
i := 0;

while i < crypt.NumSignerCerts do
  begin
    if (bHaveBase64) then
      begin
        digest := crypt.Pkcs7ExtractDigest(i,sbBase64.GetAsString());
      end
    else
      begin
        digest := crypt.Pkcs7ExtractDigest(i,pkcs7Data.GetEncoded('base64'));
      end;
    if (crypt.LastMethodSuccess <> 1) then
      begin
        Memo1.Lines.Add(crypt.LastErrorText);
        Exit;
      end;
    Memo1.Lines.Add('Signer ' + IntToStr(i + 1) + ' digest = ' + digest);
    i := i + 1;
  end;
end;