MRPG MRPG - 6 months ago 39
Vb.net Question

Verify signed XML document using X509 Certificate2 in vb.net

Private Sub VerifyButton_Click(sender As Object, e As EventArgs) Handles VerifyButton.Click


' Create a new XML document.
'
Dim xmlDocument As New XmlDocument

' Format using white spaces.
'
xmlDocument.PreserveWhitespace = True

' Load the passed XML file into the document.
'
xmlDocument.LoadXml(ToVerifyTextBox.Text)

' Create a new SignedXml object and pass it the XML document class.
'
Dim signedXml As New SignedXml(xmlDocument)

' Find the “Signature” node and create a new XmlNodeList object.
'
Dim nodeList As XmlNodeList = xmlDocument.GetElementsByTagName("Signature", "http://www.w3.org/2000/09/xmldsig#")


If nodeList.Count <= 0 Then
MessageBox.Show("Verification failed: No Signature was found in the document.")

' This example only supports one signature for
' the entire XML document. Throw an exception
' if more than one signature was found.
ElseIf nodeList.Count >= 2 Then
MessageBox.Show("Verification failed: More that one signature was found for the document.")
Else

' Load the signature node.
'
signedXml.LoadXml(CType(nodeList(0), XmlElement))

' Check the signature and show the result.
'
If signedXml.CheckSignature() Then
MessageBox.Show("Signature verified!")
Else
MessageBox.Show("Invalid signature!!!")
End If
End If

End Sub


This code will go trough the xml file and find the tag signature and the signature verified as valid, but I want to check and compare the key with the key in the xml file and if it is ok than to signature verified as valid.

Answer

I resolved this.

This is my code that I use to verify xml document:

Public Function VerifyXml(Doc As XmlDocument, Key As String) As Boolean

    Dim tmpRsa As New RSACryptoServiceProvider()

    tmpRsa.FromXmlString(Key)

    'VERIFY ALL ARGUMENTS HAVE BEEN PASSED IN 
    If Doc Is Nothing Then

        Throw New ArgumentException("Doc")
    End If

    If Key Is Nothing Then

        Throw New ArgumentException("Key")
    End If

    'HOLD THE SIGNED DOCUMENT 
    Dim signedXml As New SignedXml(Doc)

    'LOCATE THE SIGNATURE NODE IN THE DOCUMENT 
    Dim nodeList As XmlNodeList = Doc.GetElementsByTagName("Signature")

    'IF WE CANT FIND THE NODE THEN THIS DOCUMENT IS NOT SIGNED 
    If nodeList.Count <= 0 Then
        Throw New CryptographicException("Verification failed: No Signature was found in the document.")
    End If

    'IF THERE ARE MORE THEN ONE SIGNATURES THEN FAIL  
    If nodeList.Count >= 2 Then
        Throw New CryptographicException("Verification failed: More that one signature was found for the document.")
    End If

    'LOAD THE SIGNATURE NODE INTO THE SIGNEDXML DOCUMENT  
    signedXml.LoadXml(DirectCast(nodeList(0), XmlElement))

    'CHECK THE SIGNATURE AND SEND THE RESULT  
    Return signedXml.CheckSignature(tmpRsa)

End Function
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