(PureBasic) Create XML Signature with External Data Reference

Demonstrates how to create an XML digital signature where the data is external. In this case, the data is a JPG file.

This example requires Chilkat v9.5.0.69 or greater.

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IncludeFile "CkXmlDSigGen.pb"
IncludeFile "CkHttp.pb"
IncludeFile "CkStringBuilder.pb"
IncludeFile "CkPrivateKey.pb"
IncludeFile "CkBinData.pb"

Procedure ChilkatExample()

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

    ; This example inserts an XML signature in the following XML:

    ; <?xml version="1.0" encoding="UTF-8" standalone="no"?>
    ; <abc>
    ;   <xyz>
    ;     <jpg>
    ;         <name>starfish.jpg</name>
    ;         <url>https://www.chilkatsoft.com/images/starfish.jpg</url>
    ;     </jpg>
    ;   </xyz>
    ; </abc>

    ; The above XML is available at https://www.chilkatsoft.com/exampleData/addSignatureToThis.xml
    ; First fetch the XML:

    url.s = "https://www.chilkatsoft.com/exampleData/addSignatureToThis.xml"
    http.i = CkHttp::ckCreate()
    If http.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 = CkHttp::ckQuickGetSb(http,url,sbXml)
    If success <> 1
        Debug CkHttp::ckLastErrorText(http)
        CkHttp::ckDispose(http)
        CkStringBuilder::ckDispose(sbXml)
        ProcedureReturn
    EndIf

    ; We'll use an RSA private key for signing.  
    rsaKey.i = CkPrivateKey::ckCreate()
    If rsaKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkPrivateKey::ckLoadPemFile(rsaKey,"qa_data/rsa/rsaPrivKey_pkcs8.pem")
    If success <> 1
        Debug CkPrivateKey::ckLastErrorText(rsaKey)
        CkHttp::ckDispose(http)
        CkStringBuilder::ckDispose(sbXml)
        CkPrivateKey::ckDispose(rsaKey)
        ProcedureReturn
    EndIf

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

    ; Indicate were the Signature will be inserted:
    CkXmlDSigGen::setCkSigLocation(xmlSigGen, "abc|xyz|jpg")

    ; Provide the RSA key to be used for signing:
    CkXmlDSigGen::ckSetPrivateKey(xmlSigGen,rsaKey)

    ; Fetch the JPG image data.
    jpgUrl.s = "https://www.chilkatsoft.com/images/starfish.jpg"
    jpgData.i = CkBinData::ckCreate()
    If jpgData.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkHttp::ckQuickGetBd(http,jpgUrl,jpgData)
    If success <> 1
        Debug CkHttp::ckLastErrorText(http)
        CkHttp::ckDispose(http)
        CkStringBuilder::ckDispose(sbXml)
        CkPrivateKey::ckDispose(rsaKey)
        CkXmlDSigGen::ckDispose(xmlSigGen)
        CkBinData::ckDispose(jpgData)
        ProcedureReturn
    EndIf

    ; Add the external data reference:
    CkXmlDSigGen::ckAddExternalBinaryRef(xmlSigGen,jpgUrl,jpgData,"sha256","")

    ; Create the XML digital signature:
    success = CkXmlDSigGen::ckCreateXmlDSigSb(xmlSigGen,sbXml)
    If success <> 1
        Debug CkXmlDSigGen::ckLastErrorText(xmlSigGen)
        CkHttp::ckDispose(http)
        CkStringBuilder::ckDispose(sbXml)
        CkPrivateKey::ckDispose(rsaKey)
        CkXmlDSigGen::ckDispose(xmlSigGen)
        CkBinData::ckDispose(jpgData)
        ProcedureReturn
    EndIf

    ; Examine the XML that now contains the Signature:
    Debug CkStringBuilder::ckGetAsString(sbXml)

    ; <?xml version="1.0" encoding="UTF-8" standalone="no"?>
    ; <abc>
    ;   <xyz>
    ;     <jpg>
    ;         <name>starfish.jpg</name>
    ;         <url>https://www.chilkatsoft.com/images/starfish.jpg</url>
    ;     <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#"><ds:SignedInfo><ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/><ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/><ds:Reference URI="https://www.chilkatsoft.com/images/starfish.jpg"><ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/><ds:DigestValue>AOU810yJV5Np/DnO29qpObqiTSTTCDvxGsX5ayiTYXI=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>ApHRr6nilNrzt3dLveC9zlPoSllaCMfHsbAwr+vYBPkHkJ4wD5LzDDhi1tSJZAAeTckmvSqIG3Wi0rgXQiSM644MD3coBFx4QgrY+GZ+XJJE2Y0Ye3VvaQBiRdUW3INGsW4GLubncgQk5JhuAQjo6O/GKpfEuYqUJj/6CLHLQwMPwbZ2043ykgzuPFoOZf6EydJMBAn1ORMvrpUn+zuA9UngOTGap6eWE4CeiNx23BRC2wSztbUjdCLcqXvgiYu/v0tBNaTcwy7b6+IFtwv/lNUUBUQJ/3p+aErzFn3wLeH3yeqpDCU0U6Dqu5SS1jYupcWWsLHJjYnj2066DPJi/g==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:RSAKeyValue><ds:Modulus>sXeRhM55P13FbpNcXAMR3olbw2Wa6keZIHu5YTZYUBTlYWId+pNiwUz3zFIEo+0IfYR0H27ybIycQO+1IIzJofUFNMAL3tZps2OKPlsjuCPls6kXpXhv/gvhux8LrCtp4PcKWqJ6QVOZKChc7WAx40qFWzHi57ueqRTv3x0kESqGg/VjsqyTEvb55psJO2RsfhLT7+YVh3hImRM3RDaJdkTkPuOxeFyT6N7VXD09329sLuS3QkUbE9zEKDnz9X3d8dEQdJhSI9ba5fxl8R7fu8pB67ElfzFml96X1jLFtzy1pzOT5Fc4ROcaqlYckVzdBq9sxezm6MYmDBjNAcibRw==</ds:Modulus><ds:Exponent>AQAB</ds:Exponent></ds:RSAKeyValue></ds:KeyValue></ds:KeyInfo></ds:Signature></jpg>
    ;   </xyz>
    ; </abc>
    ; 


    CkHttp::ckDispose(http)
    CkStringBuilder::ckDispose(sbXml)
    CkPrivateKey::ckDispose(rsaKey)
    CkXmlDSigGen::ckDispose(xmlSigGen)
    CkBinData::ckDispose(jpgData)


    ProcedureReturn
EndProcedure