(Swift 3,4,5...) Validate Certificate using OCSP Protocol

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

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func chilkatTest() {
    // 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.
    let cert = CkoCert()!
    var success: Bool = cert.load(fromFile: "qa_data/certs/google.crt")
    if success != true {
        print("\(cert.lastErrorText!)")
        return
    }

    // Get the cert's OCSP URL.
    var ocspUrl: String? = cert.ocspUrl

    // Build the JSON that will be the OCSP request.

    // Possible hash algorithms are sha1, sha256, sha384, sha512.  
    var hashAlg: String? = "sha256"
    let prng = CkoPrng()!
    let json = CkoJsonObject()!
    json.emitCompact = false
    // Read more about OCSP nonce lengths
    json.update("extensions.ocspNonce", value: prng.genRandom(16, encoding: "base64"))
    json.i = 0
    json.update("request[i].cert.hashAlg", value: hashAlg)
    json.update("request[i].cert.issuerNameHash", value: cert.hash(of: "IssuerDN", hashAlg: hashAlg, encoding: "base64"))
    json.update("request[i].cert.issuerKeyHash", value: cert.hash(of: "IssuerPublicKey", hashAlg: hashAlg, encoding: "base64"))
    json.update("request[i].cert.serialNumber", value: cert.serialNumber)

    print("\(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"
    //       }
    //     }
    //   ]
    // }

    let ocspRequest = CkoBinData()!
    let http = CkoHttp()!

    // Convert our JSON to a binary (ASN.1) OCSP request
    success = http.createOcspRequest(json, ocspRequest: ocspRequest)
    if success == false {
        print("\(http.lastErrorText!)")
        return
    }

    // Send the OCSP request to the OCSP server
    var resp: CkoHttpResponse? = http.pBinaryBd("POST", url: ocspUrl, data: ocspRequest, contentType: "application/ocsp-request", md5: false, gzip: false)
    if http.lastMethodSuccess != true {
        print("\(http.lastErrorText!)")
        return
    }

    // Get the binary (ASN.1) OCSP reply
    let ocspReply = CkoBinData()!
    resp!.getBodyBd(ocspReply)
    resp = nil

    // Convert the binary reply to JSON.
    // Also returns the overall OCSP response status.
    let jsonReply = CkoJsonObject()!
    var ocspStatus: Int = http.parseOcspReply(ocspReply, replyData: jsonReply).intValue

    // 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 {
        print("Invalid OCSP reply.")
        return
    }

    print("Overall OCSP Response Status: \(ocspStatus)")

    // Let's examine the OCSP response (in JSON).
    jsonReply.emitCompact = false
    print("\(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:
    var certStatus: Int = -1
    if jsonReply.hasMember("response.cert[0].status") == true {
        certStatus = jsonReply.int(of: "response.cert[0].status").intValue
    }

    // Possible certStatus values are:
    // -1: No status returned.
    // 0: Good
    // 1: Revoked
    // 2: Unknown.
    print("Certificate Status: \(certStatus)")

}