(CkPython) 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.)

Chilkat Python Downloads install with pip pip3 install chilkat or download... Python Module for Windows, MacOS, Linux, Alpine Linux, Solaris

import sys
import chilkat

# 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.
sbXml = chilkat.CkStringBuilder()
success = sbXml.LoadFile("c:/someDir/fileToSign.xml","utf-8")
if (success == False):
    print("Failed to load XML file.")
    sys.exit()

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

gen = chilkat.CkXmlDSigGen()
gen.put_SigLocation("Saa:DataPDU|LAU")
gen.put_SigLocationMod(0)
gen.put_SigNamespacePrefix("ds")
gen.put_SigNamespaceUri("http://www.w3.org/2000/09/xmldsig#")
gen.put_SignedInfoCanonAlg("EXCL_C14N")
gen.put_SignedInfoDigestMethod("sha256")
gen.put_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):
    print(gen.lastErrorText())
    sys.exit()

# Examine the signed XML
print(sbXml.getAsString())

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