(Swift 3,4,5...) Alliance Access LAU Sign Message (XML Signature using HMAC-SHA-256)

Demonstrates how to sign XML according to the requirements for Alliance Access LAU (Local Authentication) using HMAC-SHA-256.

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func chilkatTest() {
    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // We begin with this message:

    // <?xml version="1.0" encoding="utf-8"?>
    // <Saa:DataPDU xmlns:Saa="urn:swift:saa:xsd:saa.2.0" xmlns:Sw="urn:swift:snl:ns.Sw"
    //   xmlns:SwGbl="urn:swift:snl:ns.SwGbl" xmlns:SwInt="urn:swift:snl:ns:SwInt" xmlns:SwSec="url:swift:snl:ns.SwSec">
    //     <Saa:Revision>2.0.7</Saa:Revision>
    //     <Saa:Header>
    //         <Saa:Message>
    // 			<test>blah blah</test>
    //         </Saa:Message>
    //     </Saa:Header>
    //     <Saa:Body>...</Saa:Body>
    //     <Saa:LAU>
    //     </Saa:LAU>
    // </Saa:DataPDU>

    // And we want so sign to create this as the result:
    // The signed XML we'll create will not be indented and pretty-printed like this.
    // Instead, we'll use the "CompactSignedXml" behavior to produce compact single-line XML.

    // <?xml version="1.0" encoding="utf-8"?>
    // <Saa:DataPDU xmlns:Saa="urn:swift:saa:xsd:saa.2.0" xmlns:Sw="urn:swift:snl:ns.Sw"
    //   xmlns:SwGbl="urn:swift:snl:ns.SwGbl" xmlns:SwInt="urn:swift:snl:ns:SwInt" xmlns:SwSec="url:swift:snl:ns.SwSec">
    //     <Saa:Revision>2.0.7</Saa:Revision>
    //     <Saa:Header>
    //         <Saa:Message>
    // 			<test>blah blah</test>
    //         </Saa:Message>
    //     </Saa:Header>
    //     <Saa:Body>...</Saa:Body>
    //     <Saa:LAU>
    //         <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#hmac-sha256"/>
    //                 <ds:Reference URI="">
    //                     <ds:Transforms>
    //                         <ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/>
    //                         <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
    //                     </ds:Transforms>
    //                     <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
    //                     <ds:DigestValue>Y7oScHnYOUQvni/TSzZbDec+HR+mWIFH149GXpwj1Ws=</ds:DigestValue>
    //                 </ds:Reference>
    //             </ds:SignedInfo>
    //             <ds:SignatureValue>6ynF/FcwbPsHrtlj3h2agJigdnvpbO6hOzKSRGzqkw0=</ds:SignatureValue>
    //         </ds:Signature>
    //     </Saa:LAU>
    // </Saa:DataPDU>

    var success: Bool = true

    // Create the XML to be signed...

    // (The XML does not need to be created this way.  It can be loaded from a file or a string.)
    // Also, use this online tool to generate code from sample XML: 
    // Generate Code to Create XML

    let xmlToSign = CkoXml()!
    xmlToSign.tag = "Saa:DataPDU"
    xmlToSign.addAttribute("xmlns:Saa", value: "urn:swift:saa:xsd:saa.2.0")
    xmlToSign.addAttribute("xmlns:Sw", value: "urn:swift:snl:ns.Sw")
    xmlToSign.addAttribute("xmlns:SwGbl", value: "urn:swift:snl:ns.SwGbl")
    xmlToSign.addAttribute("xmlns:SwInt", value: "urn:swift:snl:ns:SwInt")
    xmlToSign.addAttribute("xmlns:SwSec", value: "url:swift:snl:ns.SwSec")
    xmlToSign.updateChildContent("Saa:Revision", value: "2.0.7")
    xmlToSign.updateChildContent("Saa:Header|Saa:Message|test", value: "blah blah")
    xmlToSign.updateChildContent("Saa:Body", value: "...")
    xmlToSign.updateChildContent("Saa:LAU", value: "")

    let gen = CkoXmlDSigGen()!

    gen.sigLocation = "Saa:DataPDU|Saa:LAU"
    gen.sigLocationMod = 0
    gen.sigNamespacePrefix = "ds"
    gen.sigNamespaceUri = "http://www.w3.org/2000/09/xmldsig#"
    gen.signedInfoCanonAlg = "EXCL_C14N"
    gen.signedInfoDigestMethod = "sha256"

    // You may alternatively choose "IndentedSignature" instead of "CompactSignedXml"
    gen.behaviors = "CompactSignedXml"

    gen.addSameDocRef("", digestMethod: "sha256", canonMethod: "EXCL_C14N", prefixList: "", refType: "")

    // Specify the HMAC key.
    // For example, if the HMAC key is to be the us-ascii bytes of the string "secret",
    // the HMAC key can be set in any of the following ways (and also more ways not shown here..)
    gen.setHmacKey("secret", encoding: "ascii")
    // or
    gen.setHmacKey("c2VjcmV0", encoding: "base64")
    // or
    gen.setHmacKey("736563726574", encoding: "hex")

    // Sign the XML..
    let sbXml = CkoStringBuilder()!
    xmlToSign.getSb(sbXml)
    success = gen.createXmlDSigSb(sbXml)
    if success != true {
        print("\(gen.lastErrorText!)")
        return
    }

    // Save the signed XML to a file.
    success = sbXml.writeFile("qa_output/signedXml.xml", charset: "utf-8", emitBom: false)

    // Show the signed XML.
    print("\(sbXml.getAsString()!)")

}