(Delphi ActiveX) Validate Certificate using OCSP Protocol

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

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
cert: TChilkatCert;
success: Integer;
ocspUrl: WideString;
hashAlg: WideString;
prng: TChilkatPrng;
json: TChilkatJsonObject;
ocspRequest: TChilkatBinData;
http: TChilkatHttp;
resp: IChilkatHttpResponse;
ocspReply: TChilkatBinData;
jsonReply: TChilkatJsonObject;
ocspStatus: Integer;
certStatus: Integer;

begin
// 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.
cert := TChilkatCert.Create(Self);
success := cert.LoadFromFile('qa_data/certs/google.crt');
if (success <> 1) then
  begin
    Memo1.Lines.Add(cert.LastErrorText);
    Exit;
  end;

// Get the cert's OCSP URL.
ocspUrl := cert.OcspUrl;

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

// Possible hash algorithms are sha1, sha256, sha384, sha512.  
hashAlg := 'sha256';
prng := TChilkatPrng.Create(Self);
json := TChilkatJsonObject.Create(Self);
json.EmitCompact := 0;
// 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);

Memo1.Lines.Add(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"
//       }
//     }
//   ]
// }

ocspRequest := TChilkatBinData.Create(Self);
http := TChilkatHttp.Create(Self);

// Convert our JSON to a binary (ASN.1) OCSP request
success := http.CreateOcspRequest(json.ControlInterface,ocspRequest.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(http.LastErrorText);
    Exit;
  end;

// Send the OCSP request to the OCSP server
resp := http.PBinaryBd('POST',ocspUrl,ocspRequest.ControlInterface,'application/ocsp-request',0,0);
if (http.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(http.LastErrorText);
    Exit;
  end;

// Get the binary (ASN.1) OCSP reply
ocspReply := TChilkatBinData.Create(Self);
resp.GetBodyBd(ocspReply.ControlInterface);

// Convert the binary reply to JSON.
// Also returns the overall OCSP response status.
jsonReply := TChilkatJsonObject.Create(Self);
ocspStatus := http.ParseOcspReply(ocspReply.ControlInterface,jsonReply.ControlInterface);

// 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
  begin
    Memo1.Lines.Add('Invalid OCSP reply.');
    Exit;
  end;

Memo1.Lines.Add('Overall OCSP Response Status: ' + IntToStr(ocspStatus));

// Let's examine the OCSP response (in JSON).
jsonReply.EmitCompact := 0;
Memo1.Lines.Add(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:
certStatus := -1;
if (jsonReply.HasMember('response.cert[0].status') = 1) then
  begin
    certStatus := jsonReply.IntOf('response.cert[0].status');
  end;

// Possible certStatus values are:
// -1: No status returned.
// 0: Good
// 1: Revoked
// 2: Unknown.
Memo1.Lines.Add('Certificate Status: ' + IntToStr(certStatus));
end;