(Swift 3,4,5...) 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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func chilkatTest() {
    // 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:

    var url: String? = "https://www.chilkatsoft.com/exampleData/addSignatureToThis.xml"
    let http = CkoHttp()!
    let sbXml = CkoStringBuilder()!
    var success: Bool = http.quickGetSb(url, sbContent: sbXml)
    if success != true {
        print("\(http.lastErrorText!)")
        return
    }

    // We'll use an RSA private key for signing.  
    let rsaKey = CkoPrivateKey()!
    success = rsaKey.loadPemFile("qa_data/rsa/rsaPrivKey_pkcs8.pem")
    if success != true {
        print("\(rsaKey.lastErrorText!)")
        return
    }

    let xmlSigGen = CkoXmlDSigGen()!

    // Indicate were the Signature will be inserted:
    xmlSigGen.sigLocation = "abc|xyz|jpg"

    // Provide the RSA key to be used for signing:
    xmlSigGen.setPrivateKey(rsaKey)

    // Fetch the JPG image data.
    var jpgUrl: String? = "https://www.chilkatsoft.com/images/starfish.jpg"
    let jpgData = CkoBinData()!
    success = http.quickGetBd(jpgUrl, binData: jpgData)
    if success != true {
        print("\(http.lastErrorText!)")
        return
    }

    // Add the external data reference:
    xmlSigGen.addExternalBinaryRef(jpgUrl, content: jpgData, digestMethod: "sha256", refType: "")

    // Create the XML digital signature:
    success = xmlSigGen.createXmlDSigSb(sbXml)
    if success != true {
        print("\(xmlSigGen.lastErrorText!)")
        return
    }

    // Examine the XML that now contains the Signature:
    print("\(sbXml.getAsString()!)")

    // <?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>
    // 

}