(VB.NET) Create/Verify XML Signature with External Text Reference

See more XML Digital Signatures Examples

Demonstrates how to create an XML digital signature where the referenced data is external. In this case, the data is a text file located at the following URL: https://www.chilkatsoft.com/helloWorld.txt

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

' This example inserts an XML signature into the following XML:

' <?xml version="1.0" encoding="UTF-8" standalone="no"?>
' <abc>
'   <xyz>
' 	<name>helloWorld.txt</name>
' 	<url>https://www.chilkatsoft.com/helloWorld.txt</url>
'   </xyz>
' </abc>

' Build the above XML to be signed.
Dim xml As New Chilkat.Xml
xml.Tag = "abc"
xml.UpdateChildContent("xyz|name","helloWorld.txt")
xml.UpdateChildContent("xyz|url","https://www.chilkatsoft.com/helloWorld.txt")


Dim cert As New Chilkat.Cert

Dim success As Boolean = cert.LoadPfxFile("qa_data/pfx/test_secret.pfx","secret")
If (success = False) Then
    Debug.WriteLine(cert.LastErrorText)
    Exit Sub
End If


Dim gen As New Chilkat.XmlDSigGen

' Indicate the location within the XML the Signature will be inserted.
gen.SigLocation = "abc|xyz"


' Get the content of the text data to be referenced.
Dim http As New Chilkat.Http
Dim sbExternalTxt As New Chilkat.StringBuilder
success = http.QuickGetSb("https://www.chilkatsoft.com/helloWorld.txt",sbExternalTxt)
If (success = False) Then
    Debug.WriteLine(http.LastErrorText)
    Exit Sub
End If


success = gen.AddExternalTextRef("https://www.chilkatsoft.com/helloWorld.txt",sbExternalTxt,"utf-8",False,"sha256","")
If (success = False) Then
    Debug.WriteLine(gen.LastErrorText)
    Exit Sub
End If


' Provide the private key for signing via the certificate, and indicate that
' we want the base64 of the certificate embedded in the KeyInfo.
gen.KeyInfoType = "X509Data"
gen.X509Type = "Certificate"

Dim bUsePrivateKey As Boolean = True
success = gen.SetX509Cert(cert,bUsePrivateKey)
If (success <> True) Then
    Debug.WriteLine(gen.LastErrorText)
    Exit Sub
End If


' Indicate we want an indented signature for readability.
' This can be removed after debugging is finished..
gen.Behaviors = "IndentedSignature"

' Now create and insert the Signature
Dim sbXml As New Chilkat.StringBuilder
xml.GetXmlSb(sbXml)
success = gen.CreateXmlDSigSb(sbXml)
If (success <> True) Then
    Debug.WriteLine(gen.LastErrorText)
    Exit Sub
End If


' Examine the XML with the digital signature inserted
Debug.WriteLine(sbXml.GetAsString())

' Here is the output:

' <?xml version="1.0" encoding="utf-8"?>
' <abc>
'     <xyz>
'         <name>helloWorld.txt</name>
'         <url>https://www.chilkatsoft.com/helloWorld.txt</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/helloWorld.txt">
'       <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
'       <ds:DigestValue>f4OxZX/x/FO5LcGBSKHWXfwtSx+j1ncoSt3SABJtkGk=</ds:DigestValue>
'     </ds:Reference>
'   </ds:SignedInfo>
'   <ds:SignatureValue>syFSl...pZDiFQ==</ds:SignatureValue>
'   <ds:KeyInfo>
'     <ds:X509Data>
'       <ds:X509Certificate>MIIHAz...GwnUZWCaDE=</ds:X509Certificate>
'     </ds:X509Data>
'   </ds:KeyInfo>
' </ds:Signature></xyz>
' </abc>


' Let's verify the signature...
Dim verifier As New Chilkat.XmlDSig
success = verifier.LoadSignatureSb(sbXml)
If (success <> True) Then
    Debug.WriteLine(verifier.LastErrorText)
    Exit Sub
End If


' Let's examine the external references, and fetch the data for each..
Dim sbExternalData As New Chilkat.StringBuilder
Dim numRefs As Integer = verifier.NumReferences
Dim i As Integer = 0
While i < numRefs
    Dim bExternal As Boolean = verifier.IsReferenceExternal(i)
    If (bExternal = True) Then
        Dim uri As String = verifier.ReferenceUri(i)

        ' We're assuming the URI is an https:// or http:// URL...
        ' Let's also assume we know that the referenced data is text and we want the utf-8 byte representation.
        sbExternalData.Clear()
        success = http.QuickGetSb(uri,sbExternalData)
        If (success = False) Then
            Debug.WriteLine(http.LastErrorText)
            Exit Sub
        End If


        success = verifier.SetRefDataSb(i,sbExternalData,"utf-8")
        If (success = False) Then
            Debug.WriteLine(verifier.LastErrorText)
            Exit Sub
        End If

    End If

    i = i + 1
End While

' Now that we have the external data available, we can verify the reference digest(s) and the signature.
Dim bVerified As Boolean = verifier.VerifySignature(True)
If (bVerified <> True) Then
    Debug.WriteLine(verifier.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("Signature verified!")