Pascal (Lazarus/Delphi)
Decrypt a govtalk.gov.uk SOAP GovTalkMessage

Demonstrates how to decrypt the content contained in the XML of a GovTalkMessage SOAP response.
Chilkat Pascal (Lazarus/Delphi) Downloads

Download Chilkat for Pascal (Lazarus/Delphi)
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.BinData,
  Chilkat.Xml,
  Chilkat.Crypt2,
  Chilkat.Cert;

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

procedure RunDemo;
var
  success: Boolean;
  xml: TXml;
  Body: string;
  cert: TCert;
  crypt: TCrypt2;
  bd: TBinData;

begin
  success := False;

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

  //  The GovTalkMessage response looks something like this:

  //  <?xml version="1.0" encoding="utf-8"?>
  //  <GovTalkMessage xmlns="http://www.govtalk.gov.uk/CM/envelope">
  //    <EnvelopeVersion>3.1</EnvelopeVersion>
  //    <Header>
  //      <MessageDetails>
  //        <Class>CSSZ_DZDPN</Class>
  //        <Qualifier>request</Qualifier>
  //        <Function>submit</Function>
  //        <TransactionID />
  //        <AuditID />
  //        <CorrelationID>aaaaa</CorrelationID>
  //        <ResponseEndPoint PollInterval="0" />
  //        <Transformation>XML</Transformation>
  //        <GatewayTest />
  //        <GatewayTimestamp />
  //      </MessageDetails>
  //      <SenderDetails>
  //        <IDAuthentication>
  //          <SenderID />
  //          <Authentication>
  //            <Method>clear</Method>
  //            <Role />
  //            <Value />
  //          </Authentication>
  //        </IDAuthentication>
  //        <X509Certificate />
  //        <EmailAddress>somebody@example.com</EmailAddress>
  //      </SenderDetails>
  //    </Header>
  //    <GovTalkDetails>
  //      <Keys>
  //        <Key Type="vars">9999999999</Key>
  //      </Keys>
  //      <GatewayAdditions>
  //        <Source>VREP</Source>
  //      </GatewayAdditions>
  //    </GovTalkDetails>
  //    <Body>
  //      <Message xmlns="http://www.cssz.cz/XMLSchema/envelope" version="1.2" eType="DZDPN20">
  //        <Header>
  //          <Signature xmlns:dt="urn:schemas-microsoft-com:datatypes" dt:dt="bin.base64">MIIJ0A ... UMw=
  //  </Signature>
  //          <Vendor productName="some product name" version="2019" />
  //        </Header>
  //        <Body xmlns:dt="urn:schemas-microsoft-com:datatypes" encrypted="yes" contentEncoding="gzip" dt:dt="bin.base64">MIIF2w ... N2vW</Body>
  //      </Message>
  //    </Body>
  //  </GovTalkMessage>

  //  We want to get the content of the Body and decrypt it.

  //  First, let's get the content of the Body XML element, which is a base64 string starting with MIIF2w...

  xml := TXml.Create;
  success := xml.LoadXmlFile('qa_data/xml/govTalkMessageResponse.xml');
  if (success = False) then
    begin
      WriteLn(xml.LastErrorText);
      Exit;
    end;

  Body := xml.GetChildContent('Body|Message|Body');
  WriteLn(Body);

  cert := TCert.Create;
  success := cert.LoadPfxFile('qa_data/pfx/govTalkMessage_aaa.pfx','aaa');
  if (success = False) then
    begin
      WriteLn(cert.LastErrorText);
      Exit;
    end;

  crypt := TCrypt2.Create;
  crypt.CryptAlgorithm := 'pki';
  success := crypt.SetDecryptCert(cert);
  if (success = False) then
    begin
      WriteLn(crypt.LastErrorText);
      Exit;
    end;

  bd := TBinData.Create;
  //  Append the bytes to bd.
  success := bd.AppendEncoded(Body,'base64');

  //  Decrypt in-place.
  success := crypt.DecryptBd(bd);
  if (success = False) then
    begin
      WriteLn(crypt.LastErrorText);
      Exit;
    end;

  //  Save the decrypted data to a file.
  success := bd.WriteFile('qa_output/out.dat');

  //  If the decrypted data is non-text (binary) then we can examine it in an encoding, such as hex:
  WriteLn('Decrypted bytes as hex: ' + bd.GetEncoded('hex'));


  xml.Free;
  cert.Free;
  crypt.Free;
  bd.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.