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