Visual FoxPro
Decrypt a govtalk.gov.uk SOAP GovTalkMessage

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

Visual FoxPro
LOCAL lnSuccess
LOCAL loXml
LOCAL lcBody
LOCAL loCert
LOCAL loCrypt
LOCAL loBd

lnSuccess = 0

*  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...

loXml = CreateObject('Chilkat.Xml')
lnSuccess = loXml.LoadXmlFile("qa_data/xml/govTalkMessageResponse.xml")
IF (lnSuccess = 0) THEN
    ? loXml.LastErrorText
    RELEASE loXml
    CANCEL
ENDIF

lcBody = loXml.GetChildContent("Body|Message|Body")
? lcBody

loCert = CreateObject('Chilkat.Cert')
lnSuccess = loCert.LoadPfxFile("qa_data/pfx/govTalkMessage_aaa.pfx","aaa")
IF (lnSuccess = 0) THEN
    ? loCert.LastErrorText
    RELEASE loXml
    RELEASE loCert
    CANCEL
ENDIF

loCrypt = CreateObject('Chilkat.Crypt2')
loCrypt.CryptAlgorithm = "pki"
lnSuccess = loCrypt.SetDecryptCert(loCert)
IF (lnSuccess = 0) THEN
    ? loCrypt.LastErrorText
    RELEASE loXml
    RELEASE loCert
    RELEASE loCrypt
    CANCEL
ENDIF

loBd = CreateObject('Chilkat.BinData')
*  Append the bytes to bd.
lnSuccess = loBd.AppendEncoded(lcBody,"base64")

*  Decrypt in-place.
lnSuccess = loCrypt.DecryptBd(loBd)
IF (lnSuccess = 0) THEN
    ? loCrypt.LastErrorText
    RELEASE loXml
    RELEASE loCert
    RELEASE loCrypt
    RELEASE loBd
    CANCEL
ENDIF

*  Save the decrypted data to a file.
lnSuccess = loBd.WriteFile("qa_output/out.dat")

*  If the decrypted data is non-text (binary) then we can examine it in an encoding, such as hex:
? "Decrypted bytes as hex: " + loBd.GetEncoded("hex")

RELEASE loXml
RELEASE loCert
RELEASE loCrypt
RELEASE loBd