B4X
Get Certificate Authority Information Access

Demonstrates how to get a certificate's Authority Information Access extension data (if it exists).
Note: This example requires Chilkat v9.5.0.76 or greater.
Chilkat B4X Downloads

B4X
Dim success As Boolean = False

Dim cert As ChilkatCert
cert.Initialize("cert")

success = cert.LoadFromFile("qa_data/certs/test_haswdt.cer")
If success <> True Then
    Log(cert.LastErrorText)
    Return
End If


'  Get the Authority Information Access extension, which is at OID 1.3.6.1.5.5.7.1.1
Dim extensionXmlStr As String = cert.GetExtensionAsXml("1.3.6.1.5.5.7.1.1")
If cert.LastMethodSuccess = False Then
    Log("Certificate does not have the AuthInfoAccess extension.")
    Return
End If


Dim xml As ChilkatXml
xml.Initialize
xml.LoadXml(extensionXmlStr)

'  See what we have..
Log(xml.GetXml)

'  We should get XML like this:

'  <?xml version="1.0" encoding="utf-8" ?>
'  <sequence>
'      <sequence>
'          <oid>1.3.6.1.5.5.7.48.2</oid>
'          <contextSpecific tag="6" constructed="0">aHR0cDovL2NydC5jb21vZG9jYS5jb20vQ09NT0RPUlNBQ2xpZW50QXV0aGVudGljYXRpb25hbmRTZWN1
'  cmVFbWFpbENBLmNydA==</contextSpecific>
'      </sequence>
'      <sequence>
'          <oid>1.3.6.1.5.5.7.48.1</oid>
'          <contextSpecific tag="6" constructed="0">aHR0cDovL29jc3AuY29tb2RvY2EuY29t</contextSpecific>
'      </sequence>
'  </sequence>

'  Typically, a certificate AIA(Authority Information access) contains 2 parts:
'  
'      On-line Certificate Status Protocol (1.3.6.1.5.5.7.48.1)
'      Certification Authority Issuer (1.3.6.1.5.5.7.48.2)
'  
'  The base64 content for each OID (in this case) is just a string.  
'  The data can be accessed and decoded like this:

Dim sbOcsp As ChilkatStringBuilder
sbOcsp.Initialize
success = xml.GetChildContentSb("/C/oid,1.3.6.1.5.5.7.48.1|++", sbOcsp)
If success = True Then
    sbOcsp.Decode("base64", "utf-8")
    Log("1.3.6.1.5.5.7.48.1:  " & sbOcsp.GetAsString)
End If


Dim sbIssuer As ChilkatStringBuilder
sbIssuer.Initialize
success = xml.GetChildContentSb("/C/oid,1.3.6.1.5.5.7.48.2|++", sbIssuer)
If success = True Then
    sbIssuer.Decode("base64", "utf-8")
    Log("1.3.6.1.5.5.7.48.2:  " & sbIssuer.GetAsString)
End If


'  The output looks like this:

'  1.3.6.1.5.5.7.48.1:  http://ocsp.comodoca.com
'  1.3.6.1.5.5.7.48.2:  http://crt.comodoca.com/COMODORSAClientAuthenticationandSecureEmailCA.crt

'  -------------------------------------------------------------------------------
'  Note: The Chilkat path passed to GetChildContentSb is composed of two commands:
'  The first command is "/C/oid,1.3.6.1.5.5.7.48.1".   It says "traverse the XML tree from the caller
'  node and stop at the 1st node having tag = "oid" and content = "1.3.6.1.5.5.7.48.1".
'  The "|" char separates the 1st command from the 2nd.
'  The 2nd command is "++" and says "move to the next sibling".