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Verify XML Signature with External Data Reference

See more XML Digital Signatures Examples

Demonstrates how to verify an XML digital signature where the data is external. In this case, the data is a JPG file.

This example requires Chilkat v9.5.0.69 or greater.

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Local $bSuccess = False

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

; The XML containing the Signature to be verified contains the following:
; <?xml version="1.0" encoding="UTF-8" standalone="no"?>
; <abc>
;   <xyz>
;     <jpg>
;         <name>starfish.jpg</name>
;         <url>https://www.chilkatsoft.com/images/starfish.jpg</url>
;     <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#"/><ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/><ds:Reference 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:SignedInfo><ds:SignatureValue>MbHOti6nOh9DJP/u7u1+a1u0wRYIGEdaAVk5ehxqeBhcR4qvGvCQ7wLxcfDuwFG2grSg43ANxDYngLqZTeFb5nCfywcuNBQI8FrNRVY5hkyv6kDW1BVN8ot9qPYX9oHxJp1e+nMszIiSxqHX3XDI7YnvFt/0CyeO5JaQQEzXzIwqqb8iUNcH/bJzR6CrTf1hGuQ5MPorG0bRwbYPPHHzipUqHBinK8VbHobnxL7GQHAhR8k9gDD35kZcMxf/74U7pGO19ZzTbdJW5S7q4bVVxvsuU3itTbhHI60pOE14ibrjZtIrPZLVUD3TQqIIF04TChW2NXdYOo3+ij4ZnP8x+g==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:RSAKeyValue><ds:Modulus>sXeRhM55P13FbpNcXAMR3olbw2Wa6keZIHu5YTZYUBTlYWId+pNiwUz3zFIEo+0IfYR0H27ybIycQO+1IIzJofUFNMAL3tZps2OKPlsjuCPls6kXpXhv/gvhux8LrCtp4PcKWqJ6QVOZKChc7WAx40qFWzHi57ueqRTv3x0kESqGg/VjsqyTEvb55psJO2RsfhLT7+YVh3hImRM3RDaJdkTkPuOxeFyT6N7VXD09329sLuS3QkUbE9zEKDnz9X3d8dEQdJhSI9ba5fxl8R7fu8pB67ElfzFml96X1jLFtzy1pzOT5Fc4ROcaqlYckVzdBq9sxezm6MYmDBjNAcibRw==</ds:Modulus><ds:Exponent>AQAB</ds:Exponent></ds:RSAKeyValue></ds:KeyValue></ds:KeyInfo></ds:Signature></jpg>
;   </xyz>
; </abc>

; The above XML is available at https://www.chilkatsoft.com/exampleData/xmlsig_external_jpg_reference.xml
; First fetch the XML..

Local $sUrl = "https://www.chilkatsoft.com/exampleData/xmlsig_external_jpg_reference.xml"
$oHttp = ObjCreate("Chilkat.Http")
$oSbXml = ObjCreate("Chilkat.StringBuilder")
$bSuccess = $oHttp.QuickGetSb($sUrl,$oSbXml)
If ($bSuccess <> True) Then
    ConsoleWrite($oHttp.LastErrorText & @CRLF)
    Exit
EndIf

$oVerifier = ObjCreate("Chilkat.XmlDSig")

; Load the XML containing the signatures to be verified.
; Note that this particular Signature already contains the RSA public key that will be used
; for verification.
$bSuccess = $oVerifier.LoadSignatureSb($oSbXml)
If ($bSuccess <> True) Then
    ConsoleWrite($oVerifier.LastErrorText & @CRLF)
    Exit
EndIf

; Get the Reference URI, which in this case is the URL to the binary data that was hashed.
; This fetchs the URI attribute value from:  <ds:Reference URI="https://www.chilkatsoft.com/images/starfish.jpg">
Local $sRefUri = $oVerifier.ReferenceUri(0)
If ($oVerifier.LastMethodSuccess <> True) Then
    ConsoleWrite("No reference URI found." & @CRLF)
    Exit
EndIf

; Download the JPG data to be verified.
$oJpgData = ObjCreate("Chilkat.BinData")
$bSuccess = $oHttp.QuickGetBd($sRefUri,$oJpgData)
If ($bSuccess <> True) Then
    ConsoleWrite($oHttp.LastErrorText & @CRLF)
    Exit
EndIf

; Provide the JPG data to the verifier
$oVerifier.SetRefDataBd(0,$oJpgData)

; Verify the signature
Local $bVerified = $oVerifier.VerifySignature(True)
ConsoleWrite("Signature verified = " & $bVerified & @CRLF)