(VB.NET) Get Certificate CRL Distribution Points

Demonstrates how to get a certificate's CRL Distribution Points extension data (assuming it exists). In the vast majority of cases, there will be one CRL Distribution Point.

Note: This example requires Chilkat v9.5.0.76 or greater.

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Dim cert As New Chilkat.Cert

Dim success As Boolean = cert.LoadFromFile("qa_data/certs/test_haswdt.cer")
If (success <> True) Then
    Debug.WriteLine(cert.LastErrorText)
    Exit Sub
End If


'  Get the CRL Distribution Points extension, which is at OID 2.5.29.31
Dim extensionXmlStr As String = cert.GetExtensionAsXml("2.5.29.31")
If (cert.LastMethodSuccess = False) Then
    Debug.WriteLine("Certificate does not have the CDP extension.")
    Exit Sub
End If


Dim xml As New Chilkat.Xml
xml.LoadXml(extensionXmlStr)

'  See what we have..
Debug.WriteLine(xml.GetXml())

'  We should get XML like this:

'  <?xml version="1.0" encoding="utf-8" ?>
'  <sequence>
'      <sequence>
'          <contextSpecific tag="0" constructed="1">
'              <contextSpecific tag="0" constructed="1">
'                  <contextSpecific tag="6" constructed="0">aHR0cDovL2NybC5jb21vZG9jYS5jb20vQ09NT0RPUlNBQ2xpZW50QXV0aGVudGljYXRpb25hbmRTZWN1
'  cmVFbWFpbENBLmNybA==</contextSpecific>
'              </contextSpecific>
'          </contextSpecific>
'      </sequence>
'  </sequence>
' 

'  Assuming there is one CRL Distribution Point...
Dim sbDistPoint As New Chilkat.StringBuilder
success = xml.GetChildContentSb("sequence|contextSpecific|contextSpecific|contextSpecific",sbDistPoint)
If (success = True) Then
    sbDistPoint.Decode("base64","utf-8")
    Debug.WriteLine("CRL Distribution Point:  " & sbDistPoint.GetAsString())
End If


'  Sample output:
'  CRL Distribution Point:  http://crl.comodoca.com/COMODORSAClientAuthenticationandSecureEmailCA.crl