Decrypt a govtalk.gov.uk SOAP GovTalkMessage

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

#include <C_CkXml.h>
#include <C_CkCert.h>
#include <C_CkCrypt2.h>
#include <C_CkBinData.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkXml xml;
    const char *Body;
    HCkCert cert;
    HCkCrypt2 crypt;
    HCkBinData bd;

    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 = CkXml_Create();
    success = CkXml_LoadXmlFile(xml,"qa_data/xml/govTalkMessageResponse.xml");
    if (success == FALSE) {
        printf("%s\n",CkXml_lastErrorText(xml));
        CkXml_Dispose(xml);
        return;
    }

    Body = CkXml_getChildContent(xml,"Body|Message|Body");
    printf("%s\n",Body);

    cert = CkCert_Create();
    success = CkCert_LoadPfxFile(cert,"qa_data/pfx/govTalkMessage_aaa.pfx","aaa");
    if (success == FALSE) {
        printf("%s\n",CkCert_lastErrorText(cert));
        CkXml_Dispose(xml);
        CkCert_Dispose(cert);
        return;
    }

    crypt = CkCrypt2_Create();
    CkCrypt2_putCryptAlgorithm(crypt,"pki");
    success = CkCrypt2_SetDecryptCert(crypt,cert);
    if (success == FALSE) {
        printf("%s\n",CkCrypt2_lastErrorText(crypt));
        CkXml_Dispose(xml);
        CkCert_Dispose(cert);
        CkCrypt2_Dispose(crypt);
        return;
    }

    bd = CkBinData_Create();
    // Append the bytes to bd.
    success = CkBinData_AppendEncoded(bd,Body,"base64");

    // Decrypt in-place.
    success = CkCrypt2_DecryptBd(crypt,bd);
    if (success == FALSE) {
        printf("%s\n",CkCrypt2_lastErrorText(crypt));
        CkXml_Dispose(xml);
        CkCert_Dispose(cert);
        CkCrypt2_Dispose(crypt);
        CkBinData_Dispose(bd);
        return;
    }

    // Save the decrypted data to a file.
    success = CkBinData_WriteFile(bd,"qa_output/out.dat");

    // If the decrypted data is non-text (binary) then we can examine it in an encoding, such as hex:
    printf("Decrypted bytes as hex: %s\n",CkBinData_getEncoded(bd,"hex"));


    CkXml_Dispose(xml);
    CkCert_Dispose(cert);
    CkCrypt2_Dispose(crypt);
    CkBinData_Dispose(bd);

    }