[Plugin Request] Anti-dll injection

[P4ulo]

Hello,

I need an plugin to block dll injection...

can you create one?

thanks!!!!!!

[Enigma]

Hi P4ulo, something can be done, but it depends on a result you would like to get.

Do you want to avoid injection of particular dll, or just any dll? And it is better to know the method of the dll injection.

[P4ulo]

Hi Enigma,
I want to avoid the injection of any dll other than the system...
I guess that method is LdrLoadDll and LoadLibrary..

I've found a code on the web, but depending on the time that I inject the dll with this code, still blocks some dlls needed in the game, and crash:

Code: Select all

procedure hook(target, newfunc:pointer);
var
  jmpto:dword;
    OldProtect: Cardinal; // old protect in memory
begin
  jmpto:=dword(newfunc)-dword(target)-5;
  VirtualProtect(target, 5, PAGE_EXECUTE_READWRITE, @OldProtect);
  pbyte(target)^:=$e9;
  pdword(dword(target)+1)^:=jmpto;
end;

procedure myLdrLoadDll(PathToFile:PAnsiChar; Flags:variant; ModuleFileName:PAnsiChar; var ModuleHandle:THandle);
begin
  MessageBox(0, 'I have blocked your attempt to inject a dll file!!', 'WARNING!', MB_OK);
  ModuleHandle:=0;
end;

procedure Main;
begin
Hook(GetProcAddress(GetModuleHandle('ntdll.dll'), 'LdrLoadDll'), @myLdrLoadDll);
end;


begin
end.

Can you do something?

thanks

[Enigma]

This probably one of the methods that allows to avoid injection.

There is a mistake implementing of function myLdrLoadDll. There you have to check the name of the dll that is being injected, and if this dll is not on the list of "trusted" dlls then return a zero handle.

For example,

Code: Select all

procedure myLdrLoadDll(PathToFile:PAnsiChar; Flags:variant; ModuleFileName:PAnsiChar; var ModuleHandle:THandle);
const
  ALLOWED_MODULES : array [0..2] of string = ('kernel32.dll', 'user32.dll', 'ntdll.dll');
var
  s : string;
  found : boolean;
begin
  s := LowerCase(ExtractFileName(String(PathToFile)));
  found := false;
  for i := 0 to length(ALLOWED_MODULES) do
  begin
    if s = ALLOWED_MODULES[i] then
    begin
      found := true;
      break;
    end;
  end;
  if not found then
  begin
    MessageBox(0, 'I have blocked your attempt to inject a dll file!!', 'WARNING!', MB_OK);
    ModuleHandle:=0;
  end;
end;


Also, to avoid another method of injection, you have to disable callback of function CreateRemoteThread, that is starting to run in RtlRemoteCall. I.e. get an address of the function RtlRemoteCall and write a byte $C3 to this address.

[P4ulo]

Hi Enigma,
The problem is that PathToFile only return 'C', don't return the complete path... and ModuleFileName returns nothing...

Maybe you can fix looking this: http://undocumented.ntinternals.net/Use ... adDll.html

I've tried.. without sucess

[evilbasem]

hi P4ulo

i need this plugin too i tried searching but... no helpful result goodluck ,

[Enigma]

Just noticed, the function hook method is completely wrong there..

I will try to do something and post here. Refer to this thread later.

But you have to know, there is no ideal method of anti dll injection. There are such injection methods, that no way to avoid this..

[Pls]

Hello Enigma
had any progress with this plugin?

[Enigma]

Hi Pls,

Hello Enigmahad any progress with this plugin?

As I already said, this is impossible to avoid any dll injection. There are many methods that can inject dll, and avoid all of them - impossible.

It is better and more useful to analyze what injected dll is really doing and detect it by it's work. For example, if injected dll modifies some code inside the process, we can make a plugin for Enigma that will check if this memory and, for example, terminate processes if memory is modified.

[Pls]

can you make this plugin to me with dll modifies some code inside the process

and

I compiled your example and it did not work
I edited some things to fix the hook thingy