Delphi mutual authentication

Question

I use the WinINet library to connect to a website.

Using the Internet Explorer (Win10) it works and shows me the message to select the certificate to use.

This is the delphi code I call:

FUNCTION TRAD.lastOrganization(): Integer;
VAR
  js:TlkJSONobject;
  ws: TlkJSONstring;
  url, resp: String;
  count,statusCodeLen, bodyCodeLen: Cardinal;
  header,tmp: String;
  buffer, body: String;
  statusCode: ARRAY [0 .. 1024] OF Char;
  bodyCode: ARRAY [0 .. 1024] OF Char;
  UrlHandle: HINTERNET;
BEGIN
  buffer := '00000000000000000000';
  url := contextUrl + '/rest/organization/count';
  UrlHandle := InternetOpenUrl(NetHandle, PChar(url), nil, 0, INTERNET_FLAG_RELOAD, 0);
  IF NOT ASSIGNED(UrlHandle) THEN
    SHOWMESSAGE('Unable to read the amount of Organization using the URL ' + url + ': ' +  SysErrorMessage(GetLastError));
  statusCodeLen := Length(statusCode);
  bodyCodeLen := Length(bodyCode);
  count := 0;
  IF HttpQueryInfo(UrlHandle, HTTP_QUERY_STATUS_CODE, @statusCode[0], statusCodeLen, count) THEN
  BEGIN
    buffer := statusCode;
    IF buffer <> '200' THEN
    BEGIN
      ShowMessage('While read amount of Organization I got a status code ' + buffer + ' but 200 was expected.');
      EXIT;
    END;
  END;

  count := 0;
  body := '';
  REPEAT
    FillChar(bodyCode, bodyCodeLen, 0);
    IF NOT InternetReadFile(UrlHandle, @bodyCode[0], bodyCodeLen, count) THEN
    BEGIN
      ShowMessage('Problem on reading from response stream while read the amount of Organization using the URL ' + url + '.');
      EXIT;
    END;
    IF count > 0 THEN
    BEGIN
      tmp := bodyCode;
      body := body + LeftStr(tmp, count);
    END;
  UNTIL count = 0;

  InternetCloseHandle(UrlHandle);
  Result := strtoint(body);
END;

If I call the method, I get this message:

Buuut, using the Edge-Browser I have to specify a certificate, and it works just great.

Question

How to specify the certificate?

Edit (new informations):

If I change the code to

FUNCTION TRAD.lastOrganization(): Integer;
VAR
  js:TlkJSONobject;
  ws: TlkJSONstring;
  url, resp: String;
  count,statusCodeLen, bodyCodeLen: Cardinal;
  header,tmp: String;
  buffer, body: String;
  statusCode: ARRAY [0 .. 1024] OF Char;
  bodyCode: ARRAY [0 .. 1024] OF Char;
  UrlHandle: HINTERNET;
BEGIN
  buffer := '00000000000000000000';
  url := contextUrl + '/rest/organization/count';
  UrlHandle := InternetOpenUrl(NetHandle, PChar(url), nil, 0, INTERNET_FLAG_RELOAD, 0);
  IF NOT ASSIGNED(UrlHandle) THEN
    raiseLastOSError();

It shows:

Answer 1

Consider the use of InternetErrorDlg

Code example:

function WebSiteConnect(const UserAgent: string; const Server: string; const Resource: string;): string;
var
  hInet: HINTERNET;
  hConn: HINTERNET;
  hReq:  HINTERNET;
  dwLastError:DWORD;

  nilptr:Pointer;
  dwRetVal:DWORD;

  bLoop: boolean;
  port:Integer;
begin
  hInet := InternetOpen(PChar(UserAgent), INTERNET_OPEN_TYPE_PRECONFIG, nil, nil, 0);
  if hInet = nil then exit;
  hConn := InternetConnect(hInet, PChar(Server), INTERNET_DEFAULT_HTTPS_PORT, nil, nil, INTERNET_SERVICE_HTTP, 0, 0);
  if hConn = nil then
  begin
    InternetCloseHandle(hInet);
    exit;
  end;
  hReq := HttpOpenRequest(hConn, 'GET', PChar(Resource), 'HTTP/1.0', nil, nil, INTERNET_FLAG_SECURE, 0);
  if hReq = nil then
  Begin
    InternetCloseHandle(hConn);
    InternetCloseHandle(hInet);
    exit;
  end;

  bLoop := true;
  while bLoop do
  begin
    if HttpSendRequest(hReq, nil, 0, nil, 0) then
      dwLastError := ERROR_SUCCESS
    else
      dwLastError:= GetLastError();

    if dwLastError = ERROR_INTERNET_CLIENT_AUTH_CERT_NEEDED then
    begin
      dwRetVal:= InternetErrorDlg(application.handle, hReq, dwLastError,
      FLAGS_ERROR_UI_FILTER_FOR_ERRORS or
      FLAGS_ERROR_UI_FLAGS_GENERATE_DATA or
      FLAGS_ERROR_UI_FLAGS_CHANGE_OPTIONS,
      nilptr );

      if dwRetVal = ERROR_INTERNET_FORCE_RETRY then
        continue
      else  // CANCEL button
      begin
        InternetCloseHandle(hReq);
        InternetCloseHandle(hConn);
        InternetCloseHandle(hInet);
        exit;
      end;
    end
    else
      bLoop := false;
  end;
  Result:= ...
end;