Dart
Decrypt a govtalk.gov.uk SOAP GovTalkMessage

Demonstrates how to decrypt the content contained in the XML of a GovTalkMessage SOAP response.
Chilkat Dart Downloads

Dart
import 'package:chilkat/chilkat.dart';

void main() {
  // 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...

  final xml = CkXml();
  try {
    xml.loadXmlFile('qa_data/xml/govTalkMessageResponse.xml');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final body = xml.getChildContent('Body|Message|Body');
  print(body);

  final cert = CkCert();
  try {
    cert.loadPfxFile('qa_data/pfx/govTalkMessage_aaa.pfx', 'aaa');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final crypt = CkCrypt2();
  crypt.cryptAlgorithm = 'pki';
  try {
    crypt.setDecryptCert(cert);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final bd = CkBinData();
  // Append the bytes to bd.
  bd.appendEncoded(body, 'base64');

  // Decrypt in-place.
  try {
    crypt.decryptBd(bd);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Save the decrypted data to a file.
  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:
  print('Decrypted bytes as hex: ${bd.getEncoded('hex')}');
}