Archive

Posts Tagged ‘hooking’

Caution Hooking SetWindowLong(Ptr)

June 22nd, 2009

Recently I’ve been doing a lot of bug fixes for Hades in order to increase compatiability with a number of Valve’s games. During this time I came across a bug that fixed a LOT of issues I was having. Currently Hades hooks SetWindowLong and SetWindowLongPtr in order to prevent the game subclassing the window and inserting a custom window procedure above the one owned by Hades. The reason this needs to be done is so that I can ensure Hades always gets ‘first dibs’ on input into the game.

I noticed though that this was causing problems with a number of Valve’s games. After reading over my code for a bit I came across the bug which was obvious in hindsight yet seemed innocent enough at the time. When implementing the hook I got a little lazy, and rather than subclassing only the window handles passed in by the D3D layer, I was just hooking ALL windows that were being passed into the API. Needless to say this is NOT a good idea and can cause great instability.

Low and behold as soon as I filtered it just to rendering windows the issues went away and a handful of games ‘magically’ started working properly.

Whilst I’m much too lazy to actually debug it to the point where I can work out which window was causing issues and why, it suffices to say that it’s probably a bad idea to hook any more windows than you actually need.

Screenshots of the newly supported games:

WoWMimic v47 Changes

May 27th, 2009

Many of you will know by now that WoWMimic v47 is out. A few interesting changes, nothing really substantial though.

  1. GetCursorPos and SetCursorPos are now also hooked using VEH.
  2. ZwQueryVirtualMemory is now hooked at the return statement so values are modified AFTER the function is called. They have fixed one hole, but introduced another. Still hooked with VEH.
  3. ZeGetContextThread hook is still present but not longer activated. They have also updated their hook body, fixing one hole, but again, introducing another (see if you can spot it).
  4. They have implemented some VERY lame ‘obfuscation’ attempts. Really quite a poor job, 5 minutes tops to figure out the mess, or 30 or so seconds if you know what you’re looking at.

All in all quite disappointing. They broke the previous version of WardenMimic but only because they changed the offset at which they were hooking, and I was being nice and lowering the false positive rate by putting in lots of checks to detect only that exact build. Anyway, new WardenMimic incoming soon (when I don’t feel lazy).

Update:

Thanks to Harko for pointing out that GetCursorPos and SetCursorPos are still hooked with JMP hooks. It seems they implemented support for it in their VEH but didn’t actually hook it using VEH for some reason. Much like their unused changes to NtGetContextThread. Kinda retarded really….

Full code:

PrivatePaste Copy

; MimicVectoredHandler

169B379E | 55            | PUSH    EBP                         | ; Standard stack frame setup

169B379F | 8BEC          | MOV     EBP, ESP                    | ; Standard stack frame setup

169B37A1 | 81C4 00FFFFFF | ADD     ESP, -100                   | ; Sub ESP 100. Room for local variables.

169B37A7 | 60            | PUSHAD                              | ; Preserve all registers

169B37A8 | E8 00000000   | CALL    169B37AD                    | ; Obfuscation. ‘Calls’ next line and pushes the address of that line onto stack.

169B37AD | 5B            | POP     EBX                         | ; Pop address (of current line) back off and into EBX

169B37AE | 81EB 75164000 | SUB     EBX, 401675                 | ; Subtract 401675 from EBX (169B37AD) (Final: 165B2138)

169B37B4 | 8B75 08       | MOV     ESI, DWORD PTR [EBP+8]      | ; Get pExceptionInfo

169B37B7 | 8B7E 04       | MOV     EDI, DWORD PTR [ESI+4]      | ; Get pExceptionInfo->pContext

169B37BA | 8B36          | MOV     ESI, DWORD PTR [ESI]        | ; Get pExceptionInfo->pExceptionRecord

169B37BC | 8B87 B8000000 | MOV     EAX, DWORD PTR [EDI+B8]     | ; Get EIP

169B37C2 | 3B83 CD104000 | CMP     EAX, DWORD PTR [EBX+4010CD] | ; Compare EIP to address of GetCursorPos.

169B37C8 | 75 0E         | JNZ     169B37D8                    | ; If not equal go to ContinueSearchRet

169B37CA | 8D83 F8164000 | LEA     EAX, DWORD PTR [EBX+4016F8] | ; Get address of GetCursorPos_Hook

169B37D0 | 8987 B8000000 | MOV     DWORD PTR [EDI+B8], EAX     | ; Move address into EIP

169B37D6 | EB 4C         | JMP     169B3824                    | ; Go to ContinueExecRet

169B37D8 | 3B83 D1104000 | CMP     EAX, DWORD PTR [EBX+4010D1] | ; Compare EIP to address of SetCursorPos

169B37DE | 75 0E         | JNZ     169B37EE                    | ; If not equal go to ContinueSearchRet

169B37E0 | 8D83 2D174000 | LEA     EAX, DWORD PTR [EBX+40172D] | ; Get address of SetCursorPos_Hook

169B37E6 | 8987 B8000000 | MOV     DWORD PTR [EDI+B8], EAX     | ; Move address into EIP

169B37EC | EB 36         | JMP     169B3824                    | ; Go to ContinueExecRet

169B37EE | 3B83 84134000 | CMP     EAX, DWORD PTR [EBX+401384] | ; Compare EIP to address of ZwQueryVirtualMemory_Retn

169B37F4 | 75 0E         | JNZ     169B3804                    | ; If not equal go to ContinueSearchRet

169B37F6 | 8D83 50174000 | LEA     EAX, DWORD PTR [EBX+401750] | ; Get address of ZwQueryVirtualMemory_Hook

169B37FC | 8987 B8000000 | MOV     DWORD PTR [EDI+B8], EAX     | ; Move address into EIP

169B3802 | EB 20         | JMP     169B3824                    | ; Go to ContinueExecRet

169B3804 | 3B83 8C134000 | CMP     EAX, DWORD PTR [EBX+40138C] | ; Compare EIP to address of ZwGetContextThread_Hook. Currently not used/enabled.

169B380A | 75 0E         | JNZ     169B381A                    | ; If not equal go to ContinueSearchRet

169B380C | 8D83 88174000 | LEA     EAX, DWORD PTR [EBX+401788] | ; Get address of ZwGetContextThread_Hook.

169B3812 | 8987 B8000000 | MOV     DWORD PTR [EDI+B8], EAX     | ; Move address into EIP

169B3818 | EB 0A         | JMP     169B3824                    | ; Go to ContinueExecRet

169B381A | 61            | POPAD                               | ; Restore registers

169B381B | B8 00000000   | MOV     EAX, 0                      | ; Move EXCEPTION_CONTINUE_SEARCH into return value

169B3820 | C9            | LEAVE                               | ; Standard function prologue

169B3821 | C2 0400       | RETN    4                           | ; Return

169B3824 | 61            | POPAD                               | ; Restore registers

169B3825 | B8 FFFFFFFF   | MOV     EAX, -1                     | ; Move EXCEPTION_CONTINUE_EXECUTION into return value

169B382A | C9            | LEAVE                               | ; Standard function prolugue

169B382B | C2 0400       | RETN    4                           | ; Return

; GetCursorPos_Hook

169B3830 | E8 00000000      | CALL    169B3835                    | ; Obfuscation. ‘Calls’ next line and pushes the address of that line onto stack.

169B3835 | 5A               | POP     EDX                         | ; Pop address (of current line) back off and into EDX

169B3836 | 81EA FD164000    | SUB     EDX, 4016FD                 | ; Subtract 4016FD from EDX (169B3835) (Final: 165B2138)

169B383C | 83BA 09104000 01 | CMP     DWORD PTR [EDX+401009], 1   | ; Compare some internal flag to 1

169B3843 | 75 15            | JNZ     169B385A                    | ;

169B3845 | 8B4C24 04        | MOV     ECX, DWORD PTR [ESP+4]      | ; Get lpPoint

169B3849 | 8B82 0D104000    | MOV     EAX, DWORD PTR [EDX+40100D] | ; Get custom mouse x

169B384F | 8901             | MOV     DWORD PTR [ECX], EAX        | ; Set lpPoint->x to custom mouse x

169B3851 | 8B82 11104000    | MOV     EAX, DWORD PTR [EDX+401011] | ; Get custom mouse y

169B3857 | 8941 04          | MOV     DWORD PTR [ECX+4], EAX      | ; Set lpPoint->y to custom mouse y

169B385A | 8B82 CD104000    | MOV     EAX, DWORD PTR [EDX+4010CD] | ; Get address of GetCursorPos

169B3860 | 83C0 02          | ADD     EAX, 2                      | ; Jump over invalid instruction

169B3863 | FFE0             | JMP     NEAR EAX                    | ; Jump to GetCursorPos (+2)

; SetCursorPos_Hook

169B3865 | E8 00000000      | CALL    169B386A                    | ; Obfuscation. ‘Calls’ next line and pushes the address of that line onto stack.

169B386A | 5A               | POP     EDX                         | ; Pop address (of current line) back off and into EDX

169B386B | 81EA 32174000    | SUB     EDX, 401732                 | ; Subtract 401732 from EDX (169B386A) (Final: 165B2138)

169B3871 | 83BA 09104000 01 | CMP     DWORD PTR [EDX+401009], 1   | ; Compare some internal flag to 1

169B3878 | 75 03            | JNZ     169B387D                    | ; Jump if not equal to RetnCallOrig

169B387A | C2 0800          | RETN    8                           | ; Return without calling original

169B387D | 8B82 D1104000    | MOV     EAX, DWORD PTR [EDX+4010D1] | ; Get address of SetCursorPos

169B3883 | 83C0 02          | ADD     EAX, 2                      | ; Jump over invalid instruction

169B3886 | FFE0             | JMP     NEAR EAX                    | ; Jump to SetCursorPos (+2)

; ZwQueryVirtualMemory_Hook

169B3888 | E8 00000000      | CALL    169B388D                    | ; Obfuscation. ‘Calls’ next line and pushes the address of that line onto stack.

169B388D | 5A               | POP     EDX                         | ; Pop address (of current line) back off and into EDX

169B388E | 81EA 55174000    | SUB     EDX, 401755                 | ; Subtract 401755 from EDX (169B388D) (Final: 165B2138)

169B3894 | 50               | PUSH    EAX                         | ; Preserve EAX

169B3895 | 8B4424 14        | MOV     EAX, DWORD PTR [ESP+14]     | ; Get pMemoryBasicInformation

169B3899 | 8B48 04          | MOV     ECX, DWORD PTR [EAX+4]      | ; Get pMemoryBasicInformation->Allocationbase

169B389C | 3B8A 21104000    | CMP     ECX, DWORD PTR [EDX+401021] | ; Compare to MimicModuleBase

169B38A2 | 75 18            | JNZ     169B38BC                    | ; If not equal jump to LocRetn

169B38A4 | C700 00000000    | MOV     DWORD PTR [EAX], 0          | ; Zero out pMemoryBasicInformation->BaseAddress

169B38AA | C740 04 00000000 | MOV     DWORD PTR [EAX+4], 0        | ; Zero out pMemoryBasicInformation->AllocationBase

169B38B1 | C740 10 00000100 | MOV     DWORD PTR [EAX+10], 10000   | ; Set pMemoryBasicInformation->State to MEM_FREE

169B38B8 | 58               | POP     EAX                         | ; Restore EAX

169B38B9 | C2 1800          | RETN    18                          | ; Return

169B38BC | 58               | POP     EAX                         | ; Restore EAX

169B38BD | C2 1800          | RETN    18                          | ; Return

; ZwGetContextThread_Hook

169B38C0 | 8B4C24 08        | MOV     ECX, DWORD PTR [ESP+8] | ; Get pContext

169B38C4 | C741 04 00000000 | MOV     DWORD PTR [ECX+4], 0   | ; Zero out DR0

169B38CB | C741 08 00000000 | MOV     DWORD PTR [ECX+8], 0   | ; Zero out DR1

169B38D2 | C741 0C 00000000 | MOV     DWORD PTR [ECX+C], 0   | ; Zero out DR2

169B38D9 | C741 10 00000000 | MOV     DWORD PTR [ECX+10], 0  | ; Zero out DR3

169B38E0 | C2 0800          | RETN    8                      | ; Return

Preventing Recursion in API Hooks

May 26th, 2009

I’m sure many have ran across the same issue I did recently, and that is that when doing API hooking of low-level functions (e.g. the NT API) code that is inserted into the hook function (e.g. logging code) will end up calling the same function and cause a stack overflow.

Greyman had a good idea which I’ve used, and put together an example for. Credits to Greyman for the idea.

Basically, you use TLS to hold a flag so that the offending code (the code causing the infinite recursion)  is only executed once per call. The following code should work under all major Windows compilers, but is using a nonstandard compiler extension so may not work cross-platform (which is not a concern for a low level project anyway). Using LdrGetProcedureAddress as an example because using any of the standard output functions will cause the recursive call (printf, std::cout, etc):

NTSTATUS NTAPI APIHook::LdrGetProcedureAddress_Hook( IN HMODULE ModuleHandle,

IN PANSI_STRING FunctionName OPTIONAL, IN WORD Ordinal OPTIONAL,

OUT PVOID *FunctionAddress )

{

// Use TLS to prevent recursive function calls when logging

static __declspec(thread) bool Logging = false;

// Get the true address of the function

NTSTATUS RetVal =

((tLdrGetProcedureAddress)(PROC)(sm_LdrGetProcedureAddress))

(ModuleHandle,FunctionName,Ordinal,FunctionAddress);

// Don’t call function recursively when logging

if (Logging)

return RetVal;

// Start logging wrapper

Logging = true;

// Function pointer

PVOID pFunc = (FunctionAddress ? *FunctionAddress : 0);

// Log API call

if (Config::Get()->ShouldLogFunctions())

{

try

{

// Guard against structured exceptions

SehGuard Guard;

// Create string from c-style string

// Note: Will thrown an access violation if c-style string isn’t a

// valid pointer

std::string FunctionNameTemp(FunctionName->Buffer);

// If we get to this point the string is valid so log it.

DBGPRNT(boost::str(boost::format(”LdrGetProcedureAddress: Module”

” = %p, Name = %s. Return = %p.\n”) %ModuleHandle

%FunctionNameTemp %pFunc).c_str());

}

catch (const SehException& /*e*/)

{

// If we get here the string is invalid so we assume it’s an

// ordinal and log it as such

DBGPRNT(boost::str(boost::format(”LdrGetProcedureAddress: Module”

” = %p,  Ordinal = %u. Return = %p.\n”) %ModuleHandle %Ordinal

%pFunc).c_str());

}

}

// End logging wrapper

Logging = false;

// Check we got a valid pointer back

if (!FunctionAddress)

return RetVal;

// Dereference pointer and get actual function pointer

FARPROC pfn = (FARPROC)(*FunctionAddress);

// Is it one of the functions that we want hooked?

APIHook* p = sm_pHead;

for (; (pfn != NULL) && (p != NULL); p = p->m_pNext)

{

if (pfn == p->m_pOrig)

{

// The address to return matches an address we want to hook

// Return the hook function address instead

pfn = p->m_pHook;

break;

}

}

return RetVal;

}

In the above code DBGPRNT is just a macro used to call ‘printf’ if a certain compiler flag is enabled, or omit the code entirely if the flag is disabled. Implemented that way for performance reasons. Irrelevant details aside though, its easy to see how the implementation and how simple it is to use. Obviously thread-safe due to the variable being thread-local so it shouldn’t interfere with anything, I’ve yet to have any problems with it. Tested on both IA-32 and AMD64.

New ‘Anti-detection’ in WoWMimic v.46

May 24th, 2009

With WoWMimic v.46 being out for a while now and still no update for my detector, I figured I’d explain some of the changes made because I’m bored.

First things first, credits to Harko and Kynox for working with me on this.

The WoWMimic devs have removed a lot of their previous API hooks and left only the following:

  • GetCursorPos
  • SetCursorPost
  • NtGetContextThread
  • NtQueryVirtualMemory

The hooks on GetCursorPos and SetCursorPos have nothing to do with anti-detection and are just there to allow them to use the mouse properly from their injected DLL, so I am not interested in those. What I am interested in is NtGetContextThread, NtQueryVirtualMemory, and their new hooking method.

Rather than use an inline jump hook like previous builds they have gotten a little smarter and use vectored exception handling by inserting an invalid instruction at the start of the APIs. The reason this is a smarter approach is that it’s harder to track down the hook functions at runtime and hence harder to hash them. A downside of this approach though is that its very easy to identify their unique hook. Also, its still possible to manually walk the VEH linked list and find their VEH and hence their hook functions. Then again, there’s nothing stopping WoW registering a VEH above mimics (which happens if you run mimic before logging in) then using that to intercept the hooked APIs and handle it before mimic can.

Currently their vectored exception handler does three things:

  • Manage the NtQueryVirtualMemory hook
  • Manage the NtGetContextThread hook
  • Manage an unknown hook (seems to be an unused hwbp hook)

Their NtQueryVirtualMemory hook is simple. It stops Warden from RVA hashing their module using its regular module scan by returning modified data pages in their module’s memory range.

The NtGetContextThred is also quite simple. It hides hardware breakpoints by overwriting the ContextFlags in the context structure passed to the API.

The third and unknown hook seems simply to be a skeleton for a hardware breakpoint hook (hence the NtGetContextThread hook). What’s interesting though is that currently it appears to be totally unused.

Whilst WoWMimic is still HIGHLY detectable (its a fairly trivial process to detect it), they are at least making some progress. Still though, it’s far from safe so don’t use it on any accounts you value.

Appendix:

In case anyone is interested, I have dumped their VectoredHandler and API hooks. They are fully commented so even if you’re not great with ASM or Windows internals it should be easy to follow. (You will want to copy all the text into a larger window because the blog has a small width and its very difficult to read the code when it’s line-wrapped)

; LONG CALLBACK VectoredHandler(PEXCEPTION_POINTERS ExceptionInfo)

23C4E9E0 | 8B4424 04          | MOV     EAX, DWORD PTR [ESP+4]    | ; Access ExceptionInfo

23C4E9E4 | 8B40 04            | MOV     EAX, DWORD PTR [EAX+4]    | ; Access ExceptionInfo->ContextRecord

23C4E9E7 | 8B88 B8000000      | MOV     ECX, DWORD PTR [EAX+B8]   | ; Access ExceptionInfo->ContextRecord->Eip

23C4E9ED | 3B0D EC1EC923      | CMP     ECX, DWORD PTR [23C91EEC] | ; Compare to some address (always zero on my machine. seems to be for an unused HWBP hook.)

23C4E9F3 | 75 12              | JNZ     23C4EA07                  | ; If not equal jump to NtQueryVirtualMemory check

23C4E9F5 | 8B0D E41EC923      | MOV     ECX, DWORD PTR [23C91EE4] | ; Get unknown address (always zero on my machine. seems to be for an unused HWBP hook.)

23C4E9FB | 8988 B8000000      | MOV     DWORD PTR [EAX+B8], ECX   | ; Move unknown address into EIP

23C4EA01 | 83C8 FF            | OR      EAX, FFFFFFFF             | ; Set return value to EXCEPTION_CONTINUE_EXECUTION

23C4EA04 | C2 0400            | RETN    4                         | ; Return

23C4EA07 | 3B0D D41EC923      | CMP     ECX, DWORD PTR [23C91ED4] | ; Check if EIP is NtQueryVirtualMemory

23C4EA0D | 75 12              | JNZ     23C4EA21                  | ; If not eual jump to NtGetContextThread check

23C4EA0F | 8B15 CC1EC923      | MOV     EDX, DWORD PTR [23C91ECC] | ; Get address of NtQueryVirtualMemory hook sub

23C4EA15 | 8990 B8000000      | MOV     DWORD PTR [EAX+B8], EDX   | ; Move address into EIP

23C4EA1B | 83C8 FF            | OR      EAX, FFFFFFFF             | ; Set return value to EXCEPTION_CONTINUE_EXECUTION

23C4EA1E | C2 0400            | RETN    4                         | ; Return

23C4EA21 | 3B0D C41EC923      | CMP     ECX, DWORD PTR [23C91EC4] | ; Check if EIP is NtGetContextThread

23C4EA27 | 75 12              | JNZ     23C4EA3B                  | ; If not equal jump to ‘return 0′

23C4EA29 | 8B0D BC1EC923      | MOV     ECX, DWORD PTR [23C91EBC] | ; Get address of NtGetContextThread hook sub

23C4EA2F | 8988 B8000000      | MOV     DWORD PTR [EAX+B8], ECX   | ; Move address into EIP

23C4EA35 | 83C8 FF            | OR      EAX, FFFFFFFF             | ; Set return value to EXCEPTION_CONTINUE_EXECUTION

23C4EA38 | C2 0400            | RETN    4                         | ; Return

23C4EA3B | 33C0               | XOR     EAX, EAX                  | ; Set return value to EXCEPTION_CONTINUE_SEARCH

23C4EA3D | C2 0400            | RETN    4                         | ; Return

; NtQueryVirtualMemory Hook

; NTSTATUS NTAPI NtQueryVirtualMemory(IN HANDLE ProcessHandle, IN PVOID BaseAddress,

;  IN MEMORY_INFORMATION_CLASS MemoryInformationClass, OUT PVOID Buffer,

;  IN ULONG Length, OUT PULONG ResultLength OPTIONAL );

23C2EA52 | 60                 | PUSHAD                            | ; Preserve registers (ESP += 0×20)

23C2EA53 | 8B4424 28          | MOV     EAX, DWORD PTR [ESP+28]   | ; Get BaseAddress (Param2)

23C2EA57 | 3B05 E01EC723      | CMP     EAX, DWORD PTR [23C71EE0] | ; Compare BaseAddress to ModuleStart

23C2EA5D | 72 10              | JB      23C2EA6F                  | ; Take jump if BaseAddress is out of module address range

23C2EA5F | 3B05 DC1EC723      | CMP     EAX, DWORD PTR [23C71EDC] | ; Compare BaseAddres to ModuleEnd

23C2EA65 | 77 08              | JA      23C2EA6F                  | ; Take jump if BaseAddress is out of module address range

23C2EA67 | C74424 28 00000000 | MOV     DWORD PTR [ESP+28], 0     | ; Move zero into BaseAddress

23C2EA6F | 61                 | POPAD                             | ; Restore registers

23C2EA70 | A1 D81EC723        | MOV     EAX, DWORD PTR [23C71ED8] | ; Run overwritten code

23C2EA75 | 8B15 D01EC723      | MOV     EDX, DWORD PTR [23C71ED0] | ; Get address of original func

23C2EA7B | FFE2               | JMP     NEAR EDX                  | ; Call original func

; NtGetContextThread Hook

; NTSTATUS NTAPI NtGetContextThread(IN HANDLE ThreadHandle, OUT PCONTEXT pContext );

23C2EAA2 | 60            | PUSHAD                            | ; Preserve registers

23C2EAA3 | 8B4424 28     | MOV     EAX, DWORD PTR [ESP+28]   | ; Get pContext (Param2)

23C2EAA7 | C700 07000100 | MOV     DWORD PTR [EAX], 10007    | ; Move 0×00010007 into pContext->ContextFlags to hide Debug Registers

23C2EAAD | 61            | POPAD                             | ; Restore registers

23C2EAAE | A1 C81EC723   | MOV     EAX, DWORD PTR [23C71EC8] | ; Run overwritten code

23C2EAB3 | 8B15 C01EC723 | MOV     EDX, DWORD PTR [23C71EC0] | ; Get address of original func

23C2EAB9 | FFE2          | JMP     NEAR EDX                  | ; Call original func