(VB.NET) Swift Alliance LAU XML Signature

Calculating the LAU for Swift Alliance File Act XML using HMAC SHA256. (The XML signature, also referred to as Local Authentication (LAU), is computed using the algorithm HMAC based on SHA-256.)

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

' We begin with the following 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:SwInt="urn:swift:snl:ns.SwInt" xmlns:SwGbl="urn:swift:snl:ns.SwGbl" xmlns:SwSec="urn:swift:snl:ns.SwSec">
'     <Saa:Revision>2.0.6</Saa:Revision>
'     <Saa:Header>
'         <Saa:Message>
'             <Saa:SenderReference>Ref760FA1234</Saa:SenderReference>
'             <Saa:MessageIdentifier>tsrv.fin.mt7xx.gteesstandbys</Saa:MessageIdentifier>
'             <Saa:Format>File</Saa:Format>
'             <Saa:SubFormat>Input</Saa:SubFormat>
'             <Saa:Sender>
'                 <Saa:DN>cn=su8,o=ptsqgbbb,o=swift</Saa:DN>
'                 <Saa:FullName>
'                     <Saa:X1>PTSQGBBBXXX</Saa:X1>
'                 </Saa:FullName>
'             </Saa:Sender>
'             <Saa:Receiver>
'                 <Saa:DN>cn=abc,ou=saa,o=xxx,o=swift</Saa:DN>
'                 <Saa:FullName>
'                     <Saa:X1>PTSXXXXXXXX</Saa:X1>
'                     <Saa:X2>saa</Saa:X2>
'                 </Saa:FullName>
'             </Saa:Receiver>
'             <Saa:InterfaceInfo>
'                 <Saa:UserReference>CRE...</Saa:UserReference>
'                 <Saa:MessageCreator>ApplicationInterface</Saa:MessageCreator>
'                 <Saa:MessageContext>Original</Saa:MessageContext>
'                 <Saa:MessageNature>Financial</Saa:MessageNature>
'             </Saa:InterfaceInfo>
'             <Saa:NetworkInfo>
'                 <Saa:Priority>Normal</Saa:Priority>
'                 <Saa:IsPossibleDuplicate>true</Saa:IsPossibleDuplicate>
'                 <Saa:Service>swift.corp.fast!x</Saa:Service>
'                 <Saa:Network>Application</Saa:Network>
'                 <Saa:SessionNr>0080</Saa:SessionNr>
'                 <Saa:SeqNr>000001</Saa:SeqNr>
'                 <Saa:SWIFTNetNetworkInfo>
'                     <Saa:RequestType>tsrv.fin.mt7xx.gteesstandbys</Saa:RequestType>
'                     <Saa:Reference>2f949999-d32e-49eb-9999-9a819b9b9c0d</Saa:Reference>
'                     <Saa:FileInfo>SwCompression=Zip</Saa:FileInfo>
'                 </Saa:SWIFTNetNetworkInfo>
'             </Saa:NetworkInfo>
'             <Saa:SecurityInfo>
'                 <Saa:SWIFTNetSecurityInfo>
'                     <Saa:FileDigestAlgorithm>SHA-256</Saa:FileDigestAlgorithm>
'                     <Saa:FileDigestValue>9tnnjIgsowPSU+ehm8Rb0J5TvZIvhCYnySzFkpur1aw=</Saa:FileDigestValue>
'                 </Saa:SWIFTNetSecurityInfo>
'             </Saa:SecurityInfo>
'             <Saa:FileLogicalName>Payload.ZIP</Saa:FileLogicalName>
'             <Saa:ExpiryDateTime>20210712074808</Saa:ExpiryDateTime>
'         </Saa:Message>
'     </Saa:Header>
'     <Saa:Body>Payload.ZIP</Saa:Body>
' </Saa:DataPDU>

' Load the XML file to be signed.
Dim sbXml As New Chilkat.StringBuilder
Dim success As Boolean = sbXml.LoadFile("c:/someDir/fileToSign.xml","utf-8")
If (success = False) Then
    Debug.WriteLine("Failed to load XML file.")
    Exit Sub
End If


' We need to add a "LAU" XML element just before the "</Saa:DataPDU>"
Dim numReplaced As Integer = sbXml.Replace("</Saa:DataPDU>","<LAU xmlns=""urn:swift:saa:xsd:saa.2.0""></LAU></Saa:DataPDU>")


Dim gen As New Chilkat.XmlDSigGen
gen.SigLocation = "Saa:DataPDU|LAU"
gen.SigLocationMod = 0
gen.SigNamespacePrefix = "ds"
gen.SigNamespaceUri = "http://www.w3.org/2000/09/xmldsig#"
gen.SignedInfoCanonAlg = "EXCL_C14N"
gen.SignedInfoDigestMethod = "sha256"
gen.Behaviors = "CompactSignedXml"

' Sign the entire document.
gen.AddSameDocRef("","sha256","EXCL_C14N","","")

' Set our HMAC key
gen.SetHmacKey("Abcdef0123456789Abcdef0123456789","ascii")

' Sign the XML:
success = gen.CreateXmlDSigSb(sbXml)
If (success = False) Then
    Debug.WriteLine(gen.LastErrorText)
    Exit Sub
End If


' Examine the signed XML
Debug.WriteLine(sbXml.GetAsString())

' Save the signed XML to a file.
success = sbXml.WriteFile("c:/someDir/signedFile.xml","utf-8",False)