PureBasic
Decrypt a govtalk.gov.uk SOAP GovTalkMessage

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

PureBasic
IncludeFile "CkBinData.pb"
IncludeFile "CkCert.pb"
IncludeFile "CkXml.pb"
IncludeFile "CkCrypt2.pb"

Procedure ChilkatExample()

    success.i = 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...

    xml.i = CkXml::ckCreate()
    If xml.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkXml::ckLoadXmlFile(xml,"qa_data/xml/govTalkMessageResponse.xml")
    If success = 0
        Debug CkXml::ckLastErrorText(xml)
        CkXml::ckDispose(xml)
        ProcedureReturn
    EndIf

    Body.s = CkXml::ckGetChildContent(xml,"Body|Message|Body")
    Debug Body

    cert.i = CkCert::ckCreate()
    If cert.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkCert::ckLoadPfxFile(cert,"qa_data/pfx/govTalkMessage_aaa.pfx","aaa")
    If success = 0
        Debug CkCert::ckLastErrorText(cert)
        CkXml::ckDispose(xml)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    crypt.i = CkCrypt2::ckCreate()
    If crypt.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkCrypt2::setCkCryptAlgorithm(crypt, "pki")
    success = CkCrypt2::ckSetDecryptCert(crypt,cert)
    If success = 0
        Debug CkCrypt2::ckLastErrorText(crypt)
        CkXml::ckDispose(xml)
        CkCert::ckDispose(cert)
        CkCrypt2::ckDispose(crypt)
        ProcedureReturn
    EndIf

    bd.i = CkBinData::ckCreate()
    If bd.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; Append the bytes to bd.
    success = CkBinData::ckAppendEncoded(bd,Body,"base64")

    ; Decrypt in-place.
    success = CkCrypt2::ckDecryptBd(crypt,bd)
    If success = 0
        Debug CkCrypt2::ckLastErrorText(crypt)
        CkXml::ckDispose(xml)
        CkCert::ckDispose(cert)
        CkCrypt2::ckDispose(crypt)
        CkBinData::ckDispose(bd)
        ProcedureReturn
    EndIf

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

    ; If the decrypted data is non-text (binary) then we can examine it in an encoding, such as hex:
    Debug "Decrypted bytes as hex: " + CkBinData::ckGetEncoded(bd,"hex")


    CkXml::ckDispose(xml)
    CkCert::ckDispose(cert)
    CkCrypt2::ckDispose(crypt)
    CkBinData::ckDispose(bd)


    ProcedureReturn
EndProcedure