(Delphi DLL) Validate Certificate using OCSP Protocol

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

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

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Prng, HttpResponse, JsonObject, Cert, Http, BinData;

...

procedure TForm1.Button1Click(Sender: TObject);
var
cert: HCkCert;
success: Boolean;
ocspUrl: PWideChar;
hashAlg: PWideChar;
prng: HCkPrng;
json: HCkJsonObject;
ocspRequest: HCkBinData;
http: HCkHttp;
resp: HCkHttpResponse;
ocspReply: HCkBinData;
jsonReply: HCkJsonObject;
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 := CkCert_Create();
success := CkCert_LoadFromFile(cert,'qa_data/certs/google.crt');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

// Get the cert's OCSP URL.
ocspUrl := CkCert__ocspUrl(cert);

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

// Possible hash algorithms are sha1, sha256, sha384, sha512.  
hashAlg := 'sha256';
prng := CkPrng_Create();
json := CkJsonObject_Create();
CkJsonObject_putEmitCompact(json,False);
// Read more about OCSP nonce lengths
CkJsonObject_UpdateString(json,'extensions.ocspNonce',CkPrng__genRandom(prng,16,'base64'));
CkJsonObject_putI(json,0);
CkJsonObject_UpdateString(json,'request[i].cert.hashAlg',hashAlg);
CkJsonObject_UpdateString(json,'request[i].cert.issuerNameHash',CkCert__hashOf(cert,'IssuerDN',hashAlg,'base64'));
CkJsonObject_UpdateString(json,'request[i].cert.issuerKeyHash',CkCert__hashOf(cert,'IssuerPublicKey',hashAlg,'base64'));
CkJsonObject_UpdateString(json,'request[i].cert.serialNumber',CkCert__serialNumber(cert));

Memo1.Lines.Add(CkJsonObject__emit(json));

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

ocspRequest := CkBinData_Create();
http := CkHttp_Create();

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

// Send the OCSP request to the OCSP server
resp := CkHttp_PBinaryBd(http,'POST',ocspUrl,ocspRequest,'application/ocsp-request',False,False);
if (CkHttp_getLastMethodSuccess(http) <> True) then
  begin
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    Exit;
  end;

// Get the binary (ASN.1) OCSP reply
ocspReply := CkBinData_Create();
CkHttpResponse_GetBodyBd(resp,ocspReply);
CkHttpResponse_Dispose(resp);

// Convert the binary reply to JSON.
// Also returns the overall OCSP response status.
jsonReply := CkJsonObject_Create();
ocspStatus := CkHttp_ParseOcspReply(http,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
  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).
CkJsonObject_putEmitCompact(jsonReply,False);
Memo1.Lines.Add(CkJsonObject__emit(jsonReply));

// 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 (CkJsonObject_HasMember(jsonReply,'response.cert[0].status') = True) then
  begin
    certStatus := CkJsonObject_IntOf(jsonReply,'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));

CkCert_Dispose(cert);
CkPrng_Dispose(prng);
CkJsonObject_Dispose(json);
CkBinData_Dispose(ocspRequest);
CkHttp_Dispose(http);
CkBinData_Dispose(ocspReply);
CkJsonObject_Dispose(jsonReply);

end;