(PureBasic) Examine KeyInfo Certificate in XML Signature

This example loads signed XML and gets the signing certificate, assuming the certificate is contained in X509Certificate within the KeyInfo.

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IncludeFile "CkCert.pb"
IncludeFile "CkXml.pb"
IncludeFile "CkStringBuilder.pb"
IncludeFile "CkXmlDSig.pb"

Procedure ChilkatExample()

    ; This example requires the Chilkat API to have been previously unlocked.
    ; See Global Unlock Sample for sample code.

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

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

    success.i = CkStringBuilder::ckLoadFile(sbXml,"c:/aaworkarea/elias/3/face_f09006808443a699d1b.xml","utf-8")
    If success <> 1
        Debug "Failed to load XML file."
        CkXmlDSig::ckDispose(dsig)
        CkStringBuilder::ckDispose(sbXml)
        ProcedureReturn
    EndIf

    success = CkXmlDSig::ckLoadSignatureSb(dsig,sbXml)
    If success <> 1
        Debug CkXmlDSig::ckLastErrorText(dsig)
        CkXmlDSig::ckDispose(dsig)
        CkStringBuilder::ckDispose(sbXml)
        ProcedureReturn
    EndIf

    ; Get the KeyInfo XML.
    xmlKeyInfo.i = CkXmlDSig::ckGetKeyInfo(dsig)
    If CkXmlDSig::ckLastMethodSuccess(dsig) <> 1
        Debug CkXmlDSig::ckLastErrorText(dsig)
        CkXmlDSig::ckDispose(dsig)
        CkStringBuilder::ckDispose(sbXml)
        ProcedureReturn
    EndIf

    Debug CkXml::ckGetXml(xmlKeyInfo)
    Debug "----"

    ; Assuming the X509Certificate is in the KeyInfo, it will look like this:

    ;   <ds:KeyInfo Id="...">
    ;     <ds:KeyValue>
    ;     ...  
    ;     <ds:X509Data>
    ;       <ds:X509Certificate>MIIHAz...</ds:X509Certificate>
    ;     </ds:X509Data>
    ;   </ds:KeyInfo>
    certBase64.s = CkXml::ckGetChildContent(xmlKeyInfo,"*:X509Data|*:X509Certificate")
    If CkXml::ckLastMethodSuccess(xmlKeyInfo) <> 1
        Debug "No X509Certificate found in the KeyInfo."
        CkXmlDSig::ckDispose(dsig)
        CkStringBuilder::ckDispose(sbXml)
        ProcedureReturn
    EndIf

    ; Load a certificate object w/ the base64.
    cert.i = CkCert::ckCreate()
    If cert.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkCert::ckLoadFromBase64(cert,certBase64)
    If success <> 1
        Debug CkCert::ckLastErrorText(cert)
        CkXmlDSig::ckDispose(dsig)
        CkStringBuilder::ckDispose(sbXml)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    ; Examine the cert..
    Debug "SubjectDN: " + CkCert::ckSubjectDN(cert)
    Debug "IssuerDN: " + CkCert::ckIssuerDN(cert)
    Debug "SerialNumber as Decimal: " + CkCert::ckSerialDecimal(cert)

    CkXml::ckDispose(xmlKeyInfo)



    CkXmlDSig::ckDispose(dsig)
    CkStringBuilder::ckDispose(sbXml)
    CkCert::ckDispose(cert)


    ProcedureReturn
EndProcedure