(Tcl) Extract SignatureValue from Signed XML

See more XML Digital Signatures Examples

Demonstrates how to extract the signature value from signed XML.

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load ./chilkat.dll

# This example will work with the following signed XML, which as been reformatted for readability.

# <?xml version="1.0" encoding="utf-8"?>
# <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
#     <SOAP-ENV:Header>
#         <wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" SOAP-ENV:mustUnderstand="1">
#             <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#">
#                         <InclusiveNamespaces xmlns="http://www.w3.org/2001/10/xml-exc-c14n#" PrefixList="wsse SOAP-ENV"/>
#                     </ds:CanonicalizationMethod>
#                     <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/>
#                     <ds:Reference URI="#Body">
#                         <ds:Transforms>
#                             <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>OwgHPZNfDkXnZsjpfzXqAcT3RV3HzmTsEy2bP44FJ0M=</ds:DigestValue>
#                     </ds:Reference>
#                 </ds:SignedInfo>
#                 <ds:SignatureValue>C+7FWngU....DJFBcdg==</ds:SignatureValue>
#                 <ds:KeyInfo>
#                     <ds:KeyValue>
#                         <ds:RSAKeyValue>
#                             <ds:Modulus>sXeRhM55P13.....NAcibRw==</ds:Modulus>
#                             <ds:Exponent>AQAB</ds:Exponent>
#                         </ds:RSAKeyValue>
#                     </ds:KeyValue>
#                 </ds:KeyInfo>
#             </ds:Signature>
#         </wsse:Security>
#     </SOAP-ENV:Header>
#     <SOAP-ENV:Body xmlns:SOAP-SEC="http://schemas.xmlsoap.org/soap/security/2000-12" SOAP-SEC:id="Body">
#         <z:FooBar xmlns:z="http://example.com"/>
#     </SOAP-ENV:Body>
# </SOAP-ENV:Envelope>

# -----------------------------------------------------------------------------------------
# There are a number of ways we can get the contents of the  <ds:SignatureValue>...</ds:SignatureValue>

set filePath "qa_data/xml_dsig_testing/sample_to_show_how_to_extract_sig.xml"

# If you know there will only be a single SignatureValue in the XML, you don't need to parse XML.
# Just do quick and simple string search..
# For example:
set sb [new_CkStringBuilder]

set success [CkStringBuilder_LoadFile $sb $filePath "utf-8"]
if {$success == 0} then {
    puts "Failed to load file."
    delete_CkStringBuilder $sb
    exit
}

set base64Sig [CkStringBuilder_getBetween $sb "SignatureValue>" "</"]
puts "base64Sig = $base64Sig"

# -----------------------------------------------------------------------------------------
# If the XML might contain multiple signatures, but the signatures will always be located in the 
# same place, then you can (beforehand) copy a sample signed XML into Chilkat's online tool
# at Generate Parsing Code from XML
# to get the path to the SignatureValue.  For example, the line of code generated for the SignatureValue
# for the above XML is:
# string ds_SignatureValue = xml.GetChildContent("SOAP-ENV:Header|wsse:Security|ds:Signature|ds:SignatureValue");

# So you can simply use that path..
set xml [new_CkXml]

set success [CkXml_LoadXmlFile $xml $filePath]
# Assume success..

set base64Sig [CkXml_getChildContent $xml "SOAP-ENV:Header|wsse:Security|ds:Signature|ds:SignatureValue"]
puts "base64Sig = $base64Sig"

# -----------------------------------------------------------------------------------------
# Or perhaps you don't know where the signature is located in the XML.
# You can search for the tag..
# xSigVal is a CkXml
set xSigVal [CkXml_SearchForTag $xml $xml "*:SignatureValue"]
if {[CkXml_get_LastMethodSuccess $xml] == 1} then {
    puts "base64Sig = [CkXml_content $xSigVal]"
    delete_CkXml $xSigVal

} else {
    puts "No SignatureValue found."
}


delete_CkStringBuilder $sb
delete_CkXml $xml