Verify permissions to run Inno Setup installer online

Question

I am looking for a code for Inno Setup, that I can use to make my setup verify my permission to install the program. This code must check a text file on a web server.

• If the file has the value "False", the setup has to cancel an installation and save the value in a registry file to cancel the it always when Internet connection is not available.
• If the file has the value "True", the setup will continue to install, and it will delete the registry file value if it exists.
• If there is no Internet and the registry value does not exist the setup will continue to install.

Answer 1

Use InitializeSetup event function to trigger your check using HTTP request.

[Code]

const
  SubkeyName = 'Software\My Program';
  AllowInstallationValue = 'Allow Installation';

function IsInstallationAllowed: Boolean;
var
  Url: string;
  WinHttpReq: Variant;
  S: string;
  ResultDWord: Cardinal;
begin
  try
    WinHttpReq := CreateOleObject('WinHttp.WinHttpRequest.5.1');
    Url := 'https://www.example.com/can_install.txt';
    WinHttpReq.Open('GET', Url, False);
    WinHttpReq.Send('');
    if WinHttpReq.Status <> 200 then
    begin
      RaiseException(
        'HTTP Error: ' + IntToStr(WinHttpReq.Status) + ' ' + WinHttpReq.StatusText);
    end
      else
    begin
      S := Trim(WinHttpReq.ResponseText);
      Log('HTTP Response: ' + S);

      Result := (CompareText(S, 'true') = 0);

      if RegWriteDWordValue(
           HKLM, SubkeyName, AllowInstallationValue, Integer(Result)) then
        Log('Cached response to registry')
      else
        Log('Error caching response to registry');
    end;
  except
    Log('Error: ' + GetExceptionMessage);
    if RegQueryDWordValue(HKLM, SubkeyName, AllowInstallationValue, ResultDWord) then
    begin
      Log('Online check failed, using cached result');
      Result := (ResultDWord <> 0);
    end
      else
    begin
      Log('Online check failed, no cached result, allowing installation by default');
      Result := True;
    end;
  end;

  if Result then Log('Can install')
    else Log('Cannot install');
end;

function InitializeSetup(): Boolean;
begin
  Result := True;
  if not IsInstallationAllowed then
  begin
    MsgBox('You cannot install this', mbError, MB_OK);
    Result := False;
  end;
end;