WTSRM2

WTSRM2

This is a continuation to my original project WTSRM and the corresponding talk.

This project was re-written in order to utilize C++17 in order to create a template that allows us to change the required functionality at compile time with ease! This is implemented as a header only file such that you can easily add it to your own projects.

Some of the features currently implemented include:

• No CRT dependencies (10KB binary)
• Unhook all Windows DLLs with either a '.text' patch using \KnownDlls\ or \System32\
• Use VirtualProtect or WriteProcessMemory for patching
• Compile time API hashing
• Remove and restore Vectored Exception Handlers
• Remove Ldr DLL notification callbacks
• Clear hardware breakpoints
• Load libraries using work items

We can configure this behaviour as follows

#define HASHING_ALGORITHM hash_string_fnv1a	// constexpr algorithm

namespace config
{
	...

	//
	// configure behaviour
	//
	inline constexpr unsigned unhooking = system32 | write_process_memory;
	inline constexpr auto work_item_load_library = true; // use a work item for LL

	//
	// configure evasive features
	//
	inline constexpr auto clear_and_restore_veh = true; // clear and restore veh
	inline constexpr auto unregister_dll_notifs = true; // LdrRegisterDllNotification
	inline constexpr auto clear_thread_hwbps = true; // clear the hwbps
}

As we utilize constexpr, we don't pay for the features we don't use as they're dead code and optimized out of the program.

Using this header

To import DLLs first we must create the hash using the DLL_HASH macro

DLL_HASH(DBGHELP, L"DBGHELP.DLL")

We then must add it to the module_address_table which acts as our internal IAT. The hash_ constant is created by the DLL_HASH macro. For non-common DLLs which aren't always loaded we must specify their name so that we can load them.

inline addr_struct<decltype(HASHING_ALGORITHM(TOKENIZEA(T))), wchar_t> module_address_table[] =
{
	{hash_NTDLL, nullptr,},
	{hash_KERNEL32, nullptr,},
	{hash_DBGHELP, nullptr, L"DBGHELP.DLL"}
};

To import functions, first we must create the function name hash and typedef using the HASH_FUNC macro

HASH_FUNC(NtUnmapViewOfSection, NTSTATUS, HANDLE, PVOID)

The first parameter is the name of the function, next is the return type, and then the arguments to the function. We are then required to add it to our api_address_table which will be populated with the current function addresses

inline addr_struct<decltype(HASHING_ALGORITHM(TOKENIZEA(T))), void> api_address_table[] =
{
	{hash_GetProcAddress, nullptr},		
	{hash_NtUnmapViewOfSection, nullptr},

If you fail to add this function to this table, the program will not crash, but will return -1 in an attempt to increase stability.

To use an API use use the API()() macro as demonstrated

API(NtWaitForSingleObject)(NtCurrentProcess(), FALSE, &timeout);

To add your own API hashing function you must use this template in order to work with the required types.

template <typename T>
constexpr auto hash_string_(const T* buffer)
{
	TRIVIAL_TYPE_CHECK()

}

Thank you to these individuals in no particular order for their ideas and contributions @peterwintrsmith @modexpblog @jonaslyk @JustasMasiulis