lazy_import

Lazy Import technique implementation to call any import in the runtime. It will be very useful for calling undocumented functions, as well as for making it difficult for a reverse engineer to analyze your binary file, more specifically - calls to various APIs. The implementation also includes call caching for speed and optimization purposes.

Currently supports and tested only: MSVC compiler, x64-x86 Debug/Release, std::c++14 - std::c++23 Supports forwarded imports like HeapAlloc() etc.

Quick example

LI(int, MessageBoxA).call(nullptr, "Hello world.", "Goodbye world...", MB_OK);

Important

With this importer you can call absolutely any export from the DLL module you need, this is useful for conveniently calling undocumented functions.

Detailed example

int main(void)
{
    // We need to load a module that contains MessageBoxA export.
    LoadLibraryA("user32.dll");

    // Creating an instance (not necessarily)
    auto instance = LI(int, MessageBoxA); // or LI_FROM(int, "user32.dll", MessageBoxA);

    // MessageBoxA default call
    int result = instance.call(nullptr, "Hello world.", "Goodbye world...", MB_OK);

    // MessageBoxA cached call
    for (int i = 0; i < 5; ++i)
        result = instance.cached_call(nullptr, "Hello world.", "Goodbye world...", MB_OK);

    // Check for return value
    std::cout << "Last MessageBoxA returned: " << result << '\n';

    return EXIT_SUCCESS;
}

🚀 Features

• Ability to cache every call.
• Ability to disable exceptions within the code.
• Doesn't leave any strings in executable memory (exclude exceptions).
• Compile-time import name hashing.
• Doesn't leave any imports in the executable.
• Header includes only <intrin.h> so that the compilation time is minimized.

🛠️ Configuration

#define	EFFECT
LAZY_IMPORT_DISABLE_FORCEINLINE	disables force inlining
LAZY_IMPORT_DISABLE_EXCEPTIONS	disables all exceptions and returns 0 if the function fails.
LAZY_IMPORT_CASE_INSENSITIVE	disables case sensitivity in the hashing algorithm
LAZY_IMPORT_DISABLE_CACHING	completely disables caching of any calls.

Warning

If you use this utility to protect imports from reverse engineering, be careful when calling redirected (forwarded) exports, because when you search for the necessary string, it will be easy to see it in runtime. If you already know which main export follows the forward declaration - call it, it will also save you from resource overhead.

IDA Pro Pseudocode Output

Build configuration: MSVC compiler, Release x64, std::c++23 std::c17, /O2 flag.

#define LAZY_IMPORT_DISABLE_EXCEPTIONS

__int64 __fastcall li_call(__int64 a1, __int64 import_hash)
{
  __int64 v2; // r14
  PVOID *v4; // rcx
  PVOID *v5; // r12
  int *v6; // r11
  __int64 v7; // rax
  _DWORD *v8; // rbp
  unsigned int v9; // eax
  __int64 v10; // rsi
  unsigned int *v11; // rdi
  __int64 v12; // r15
  __int64 v13; // r10
  char *v14; // rbx
  int v15; // eax
  char v16; // r9
  char v17; // dl
  int v18; // ecx
  int v19; // eax
  PVOID *v21; // [rsp+30h] [rbp+8h]

  v2 = 0i64;
  v4 = &NtCurrentPeb()->Ldr->Reserved2[1];
  v21 = v4;
  v5 = (PVOID *)*v4;
  if ( *v4 == v4 )
    return 0i64;
  while ( 1 )
  {
    if ( v5[12] )
    {
      v6 = (int *)v5[6];
      if ( v6 )
      {
        v7 = v6[15];
        v8 = (int *)((char *)v6 + *(unsigned int *)((char *)v6 + v7 + 136));
        if ( *(_WORD *)v6 == 23117 && (*(_WORD *)((char *)v6 + v7 + 24) != 523 || *(int *)((char *)v6 + v7 + 140)) )
        {
          v9 = v8[6];
          if ( v9 )
          {
            v10 = 0i64;
            v11 = (unsigned int *)((char *)v6 + (unsigned int)v8[8]);
            v12 = v9;
            do
            {
              LODWORD(v13) = 0;
              v14 = (char *)v6 + *v11;
              v15 = 46051127;
              v16 = *v14;
              if ( *v14 )
              {
                do
                {
                  v17 = v16 + 32;
                  v18 = v13;
                  if ( (unsigned __int8)(v16 - 65) > 0x19u )
                    v17 = v16;
                  v19 = v17 * (v13 + 46051127) + (v17 ^ v15);
                  if ( !(_DWORD)v13 )
                    v18 = 46051127;
                  v13 = (unsigned int)(v13 + 1);
                  v16 = v14[v13];
                  v15 = v17 + (v18 ^ 0x2BEAF37) * v19;
                }
                while ( v16 );
                v6 = (int *)v5[6];
              }
              if ( import_hash == v15 )
                v2 = (__int64)v6
                   + *(unsigned int *)((char *)&v6[*(unsigned __int16 *)((char *)v6 + v10 + (unsigned int)v8[9])]
                                     + (unsigned int)v8[7]);
              ++v11;
              v10 += 2i64;
              --v12;
            }
            while ( v12 );
            v4 = v21;
          }
          if ( v2 )
            break;
        }
      }
    }
    v5 = (PVOID *)*v5;
    if ( v5 == v4 )
      return 0i64;
  }
  return v2;
}

Note

If you notice any bug or error while using this repository - create an Issue, describe your problem in as much detail as possible and I will try to release a fix soon.