PureBasic

Extract SignatureValue from Signed XML

See more XML Digital Signatures Examples

Demonstrates how to extract the signature value from signed XML. PureBasic

IncludeFile "CkStringBuilder.pb"
IncludeFile "CkXml.pb"

Procedure ChilkatExample()

    success.i = 0

    ; 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>

    filePath.s = "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:
    sb.i = CkStringBuilder::ckCreate()
    If sb.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkStringBuilder::ckLoadFile(sb,filePath,"utf-8")
    If success = 0
        Debug "Failed to load file."
        CkStringBuilder::ckDispose(sb)
        ProcedureReturn
    EndIf

    base64Sig.s = CkStringBuilder::ckGetBetween(sb,"SignatureValue>","</")
    Debug "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..
    xml.i = CkXml::ckCreate()
    If xml.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkXml::ckLoadXmlFile(xml,filePath)
    ; Assume success..

    base64Sig = CkXml::ckGetChildContent(xml,"SOAP-ENV:Header|wsse:Security|ds:Signature|ds:SignatureValue")
    Debug "base64Sig = " + base64Sig

    ; -----------------------------------------------------------------------------------------
    ; Or perhaps you don't know where the signature is located in the XML.
    ; You can search for the tag..
    xSigVal.i = CkXml::ckSearchForTag(xml,xml,"*:SignatureValue")
    If CkXml::ckLastMethodSuccess(xml) = 1
        Debug "base64Sig = " + CkXml::ckContent(xSigVal)
        CkXml::ckDispose(xSigVal)

    Else
        Debug "No SignatureValue found."
    EndIf



    CkStringBuilder::ckDispose(sb)
    CkXml::ckDispose(xml)


    ProcedureReturn
EndProcedure