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xmlxpathxml-signature

enveloping XML-Signature referencing the signatures parent node by XPath

I am having trouble to find out the correct XPath-expression for an enveloped XML-Signature. example given:

<xxx>
 <bbb>
  <Signature>
       <SignedInfo>
         ...
         <Reference>
           <Transforms>
             <Transform>
               <XPath>???<XPath>
             <Transform>
           <Transforms>
           ...
         <Reference>
       <SignedInfo>
       ...
     <Signature>
 </bbb>
 <bbb>
 </bbb>
</xxx>

Each BBB may have its own signature (and XXX must not) and there is no ID-Attribute in BBB allowed. BBB can occur multiple times. So I need to tell the signature to work with its enveloping node. Sadly the schema is fix and I know not very nice, but I have to deal with it.

Maybe the here()-function ([http://www.w3.org/TR/xmldsig-filter2/#function-here) might help? My suggestion would be:

here()/../../../../../..

where it starts at the XPath-node (noted in the link) and I walk down the signature-nodes to my BBB-node, but that looks pretty messed up.

Solution

  • I got the answer to this:

    it is simply not possible to reference the enveloping parent element via a XPath expression.

    You need to use a reference ID.