(VBScript) Verify XML Signature with External URL References

Demonstrates how to verify an XML digital signature that includes references to URLs where the data to be digested is on a web server.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
'Create a Unicode (utf-16) output text file.
Set outFile = fso.CreateTextFile("output.txt", True, True)

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

' The signed XML we wish to verify contains external references such as this:

'     <ds:Reference Id="xmldsig-e7ae7ce2-9133-4d56-bd97-0a6aef738cc2-ref0" URI="https://www.chilkatsoft.com/images/starfish.jpg">
'       <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
'       <ds:DigestValue>AOU810yJV5Np/DnO29qpObqiTSTTCDvxGsX5ayiTYXI=</ds:DigestValue>
'     </ds:Reference>
'     <ds:Reference Id="xmldsig-e7ae7ce2-9133-4d56-bd97-0a6aef738cc2-ref1" URI="https://www.chilkatsoft.com/hamlet.xml">
'       <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
'       <ds:DigestValue>4sRRyWOzC7EOic4fQ9+Op1pa10DbgoBGjBvkq09LZmE=</ds:DigestValue>
'     </ds:Reference>

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.XmlDSig")
set verifier = CreateObject("Chilkat.XmlDSig")
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Http")
set http = CreateObject("Chilkat.Http")

' First load the signed XML
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.StringBuilder")
set sbSignedXml = CreateObject("Chilkat.StringBuilder")
success = sbSignedXml.LoadFile("qa_data/xml_dsig_verify/signedWithExternalUrlRefs.xml","utf-8")
If (success = 0) Then
    outFile.WriteLine("Failed to load signed XML.")
    WScript.Quit
End If

success = verifier.LoadSignatureSb(sbSignedXml)
If (success = 0) Then
    outFile.WriteLine(verifier.LastErrorText)
    WScript.Quit
End If

' Iterate over each reference.  If it is an external URL reference, download the data and provide it to the verifier.
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.StringBuilder")
set sbRefUri = CreateObject("Chilkat.StringBuilder")
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.BinData")
set bd = CreateObject("Chilkat.BinData")
numRefs = verifier.NumReferences
i = 0
Do While i < numRefs
    If (verifier.IsReferenceExternal(i) = 1) Then
        sbRefUri.Clear 
        success = sbRefUri.Append(verifier.ReferenceUri(i))
        If (sbRefUri.StartsWith("https://",0) = 1) Then
            outFile.WriteLine("External URL Reference: " & sbRefUri.GetAsString())

            ' Download the data at the URL and provide to the verifier.
            success = http.DownloadBd(sbRefUri.GetAsString(),bd)
            If (success = 0) Then
                outFile.WriteLine(http.LastErrorText)
                WScript.Quit
            End If

            success = verifier.SetRefDataBd(i,bd)
            If (success = 0) Then
                outFile.WriteLine(verifier.LastErrorText)
                WScript.Quit
            End If

        End If

    End If

    i = i + 1
Loop

' Now that we have the external data, verify the signature..
bVerified = verifier.VerifySignature(1)
If (bVerified = 0) Then
    outFile.WriteLine(verifier.LastErrorText)
End If

outFile.WriteLine("Signature verified = " & bVerified)

outFile.Close