VB.NET Requires Chilkat v11.0.0+

Validate Certificate using OCSP Protocol

See more Certificates Examples

Demonstrates how to validate a certificate (check the revoked status) using the OCSP protocol. VB.NET

Dim success As Boolean = False

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

'  This example will check the revoked status of a certificate loaded from a file.
Dim cert As New Chilkat.Cert
success = cert.LoadFromFile("qa_data/certs/google.crt")
If (success = False) Then
    Debug.WriteLine(cert.LastErrorText)
    Exit Sub
End If


'  Get the cert's OCSP URL.
Dim ocspUrl As String = cert.OcspUrl

'  Build the JSON that will be the OCSP request.

'  Possible hash algorithms are sha1, sha256, sha384, sha512.  
Dim hashAlg As String = "sha256"
Dim prng As New Chilkat.Prng
Dim json As New Chilkat.JsonObject
json.EmitCompact = False
'  Read more about OCSP nonce lengths
json.UpdateString("extensions.ocspNonce",prng.GenRandom(16,"base64"))
json.I = 0
json.UpdateString("request[i].cert.hashAlg",hashAlg)
json.UpdateString("request[i].cert.issuerNameHash",cert.HashOf("IssuerDN",hashAlg,"base64"))
json.UpdateString("request[i].cert.issuerKeyHash",cert.HashOf("IssuerPublicKey",hashAlg,"base64"))
json.UpdateString("request[i].cert.serialNumber",cert.SerialNumber)

Debug.WriteLine(json.Emit())

'  Our OCSP request looks something like this:
'  {
'    "extensions": {
'      "ocspNonce": "qZDfbpO+nUxRzz6c/SPjE5QCAsPfpkQlRDxTnGl0gnxt7iXO"
'    },
'    "request": [
'      {
'        "cert": {
'          "hashAlg": "sha1",
'          "issuerNameHash": "9u2wY2IygZo19o11oJ0CShGqbK0=",
'          "issuerKeyHash": "d8K4UJpndnaxLcKG0IOgfqZ+uks=",
'          "serialNumber": "6175535D87BF94B6"
'        }
'      }
'    ]
'  }

Dim ocspRequest As New Chilkat.BinData
Dim http As New Chilkat.Http

'  Convert our JSON to a binary (ASN.1) OCSP request
success = http.CreateOcspRequest(json,ocspRequest)
If (success = False) Then
    Debug.WriteLine(http.LastErrorText)
    Exit Sub
End If


'  Send the OCSP request to the OCSP server
Dim resp As New Chilkat.HttpResponse
success = http.HttpBd("POST",ocspUrl,ocspRequest,"application/ocsp-request",resp)
If (success = False) Then
    Debug.WriteLine(http.LastErrorText)
    Exit Sub
End If


'  Get the binary (ASN.1) OCSP reply
Dim ocspReply As New Chilkat.BinData
resp.GetBodyBd(ocspReply)

'  Convert the binary reply to JSON.
'  Also returns the overall OCSP response status.
Dim jsonReply As New Chilkat.JsonObject
Dim ocspStatus As Integer = http.ParseOcspReply(ocspReply,jsonReply)

'  The ocspStatus can have one of these values:
'  -1:  The ARG1 does not contain a valid OCSP reply.
'  0:  Successful - Response has valid confirmations..
'  1: Malformed request - Illegal confirmation request.
'  2: Internal error - Internal error in issuer.
'  3: Try later -  Try again later.
'  4: Not used - This value is never returned.
'  5: Sig required - Must sign the request.
'  6: Unauthorized - Request unauthorized.

If (ocspStatus < 0) Then
    Debug.WriteLine("Invalid OCSP reply.")
    Exit Sub
End If


Debug.WriteLine("Overall OCSP Response Status: " & ocspStatus)

'  Let's examine the OCSP response (in JSON).
jsonReply.EmitCompact = False
Debug.WriteLine(jsonReply.Emit())

'  The JSON reply looks like this:
'  (Use the online tool at https://tools.chilkat.io/jsonParse.cshtml
'  to generate JSON parsing code.)

'  {
'    "responseStatus": 0,
'    "responseTypeOid": "1.3.6.1.5.5.7.48.1.1",
'    "responseTypeName": "ocspBasic",
'    "response": {
'      "responderIdChoice": "KeyHash",
'      "responderKeyHash": "d8K4UJpndnaxLcKG0IOgfqZ+uks=",
'      "dateTime": "20180803193937Z",
'      "cert": [
'        {
'          "hashOid": "1.3.14.3.2.26",
'          "hashAlg": "SHA-1",
'          "issuerNameHash": "9u2wY2IygZo19o11oJ0CShGqbK0=",
'          "issuerKeyHash": "d8K4UJpndnaxLcKG0IOgfqZ+uks=",
'          "serialNumber": "6175535D87BF94B6",
'          "status": 0,
'          "thisUpdate": "20180803193937Z",
'          "nextUpdate": "20180810193937Z"
'        }
'      ]
'    }
'  }
'  

'  The certificate status:
Dim certStatus As Integer = -1
If (jsonReply.HasMember("response.cert[0].status") = True) Then
    certStatus = jsonReply.IntOf("response.cert[0].status")
End If


'  Possible certStatus values are:
'  -1: No status returned.
'  0: Good
'  1: Revoked
'  2: Unknown.
Debug.WriteLine("Certificate Status: " & certStatus)