(Visual FoxPro) Validate Certificate using OCSP Protocol

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

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loCert
LOCAL lnSuccess
LOCAL lcOcspUrl
LOCAL lcHashAlg
LOCAL loPrng
LOCAL loJson
LOCAL loOcspRequest
LOCAL loHttp
LOCAL loResp
LOCAL loOcspReply
LOCAL loJsonReply
LOCAL lnOcspStatus
LOCAL lnCertStatus

* Note: Requires Chilkat v9.5.0.75 or greater.

* 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.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Cert')
loCert = CreateObject('Chilkat.Cert')
lnSuccess = loCert.LoadFromFile("qa_data/certs/google.crt")
IF (lnSuccess <> 1) THEN
    ? loCert.LastErrorText
    RELEASE loCert
    CANCEL
ENDIF

* Get the cert's OCSP URL.
lcOcspUrl = loCert.OcspUrl

* Build the JSON that will be the OCSP request.

* Possible hash algorithms are sha1, sha256, sha384, sha512.  
lcHashAlg = "sha256"
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Prng')
loPrng = CreateObject('Chilkat.Prng')
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.JsonObject')
loJson = CreateObject('Chilkat.JsonObject')
loJson.EmitCompact = 0
* Read more about OCSP nonce lengths
loJson.UpdateString("extensions.ocspNonce",loPrng.GenRandom(16,"base64"))
loJson.I = 0
loJson.UpdateString("request[i].cert.hashAlg",lcHashAlg)
loJson.UpdateString("request[i].cert.issuerNameHash",loCert.HashOf("IssuerDN",lcHashAlg,"base64"))
loJson.UpdateString("request[i].cert.issuerKeyHash",loCert.HashOf("IssuerPublicKey",lcHashAlg,"base64"))
loJson.UpdateString("request[i].cert.serialNumber",loCert.SerialNumber)

? loJson.Emit()

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

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loOcspRequest = CreateObject('Chilkat.BinData')
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Http')
loHttp = CreateObject('Chilkat.Http')

* Convert our JSON to a binary (ASN.1) OCSP request
lnSuccess = loHttp.CreateOcspRequest(loJson,loOcspRequest)
IF (lnSuccess = 0) THEN
    ? loHttp.LastErrorText
    RELEASE loCert
    RELEASE loPrng
    RELEASE loJson
    RELEASE loOcspRequest
    RELEASE loHttp
    CANCEL
ENDIF

* Send the OCSP request to the OCSP server
loResp = loHttp.PBinaryBd("POST",lcOcspUrl,loOcspRequest,"application/ocsp-request",0,0)
IF (loHttp.LastMethodSuccess <> 1) THEN
    ? loHttp.LastErrorText
    RELEASE loCert
    RELEASE loPrng
    RELEASE loJson
    RELEASE loOcspRequest
    RELEASE loHttp
    CANCEL
ENDIF

* Get the binary (ASN.1) OCSP reply
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loOcspReply = CreateObject('Chilkat.BinData')
loResp.GetBodyBd(loOcspReply)
RELEASE loResp

* Convert the binary reply to JSON.
* Also returns the overall OCSP response status.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.JsonObject')
loJsonReply = CreateObject('Chilkat.JsonObject')
lnOcspStatus = loHttp.ParseOcspReply(loOcspReply,loJsonReply)

* 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 (lnOcspStatus < 0) THEN
    ? "Invalid OCSP reply."
    RELEASE loCert
    RELEASE loPrng
    RELEASE loJson
    RELEASE loOcspRequest
    RELEASE loHttp
    RELEASE loOcspReply
    RELEASE loJsonReply
    CANCEL
ENDIF

? "Overall OCSP Response Status: " + STR(lnOcspStatus)

* Let's examine the OCSP response (in JSON).
loJsonReply.EmitCompact = 0
? loJsonReply.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:
lnCertStatus = -1
IF (loJsonReply.HasMember("response.cert[0].status") = 1) THEN
    lnCertStatus = loJsonReply.IntOf("response.cert[0].status")
ENDIF

* Possible certStatus values are:
* -1: No status returned.
* 0: Good
* 1: Revoked
* 2: Unknown.
? "Certificate Status: " + STR(lnCertStatus)

RELEASE loCert
RELEASE loPrng
RELEASE loJson
RELEASE loOcspRequest
RELEASE loHttp
RELEASE loOcspReply
RELEASE loJsonReply