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Update Hook.c #2

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54 changes: 25 additions & 29 deletions HookGuard/HookGuard/Hook.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6,21 +6,17 @@ RTLDISPATCHEXCEPTION g_RtlDispatchException = NULL;
LONG64 g_TotalCalls = 0;
LONG64 g_TotalResolved = 0;

DECLSPEC_NOINLINE VOID HookBreakpoint(VOID)
{
*(UINT32*)(g_KernelBase + g_Offsets.KdDebuggerLock) = 0x0;
*(UINT32*)(g_KernelBase + g_Offsets.NtGlobalFlag) = 0x0;
__debugbreak();
}

VOID HookHandlePrivilegedInstruction(PEXCEPTION_RECORD exceptionRecord, PCONTEXT context)
DECLSPEC_NOINLINE VOID HookHandlePrivilegedInstruction(PEXCEPTION_RECORD exceptionRecord, PCONTEXT context)
{
if (exceptionRecord->ExceptionCode != STATUS_PRIVILEGED_INSTRUCTION)
{
return;
}

// mov cr3, xxx
if (*(PWORD)context->Rip != 0x220F)
{
return;
}

BYTE operand = *(PBYTE)(context->Rip + 2);
operand &= 7;
Expand All @@ -33,29 +29,35 @@ VOID HookHandlePrivilegedInstruction(PEXCEPTION_RECORD exceptionRecord, PCONTEXT
cr3.Reserved3 = 0x0;
cr3.AddressOfPageDirectory = GuardCrypt(cr3.AddressOfPageDirectory);

KdpPrint("Fixing CR3 from 0x%p to 0x%p\n", invalidCr3, cr3.AsUInt);
InterlockedIncrement64(&g_TotalResolved);
__writecr3(cr3.AsUInt);

context->Rip += 3;

g_ZwContinue(context, FALSE);

HookBreakpoint();
}

DECLSPEC_NOINLINE VOID HookFindRecord(VOID)
{
CONTEXT current;
RtlCaptureContext(&current);

CONTEXT frames[10] = { 0 };
UNWIND_HISTORY_TABLE historyTable = { 0 };

PCONTEXT frames = (PCONTEXT)ExAllocatePool2(POOL_FLAG_NON_PAGED, sizeof(CONTEXT) * 10, 'dGkH');
if (!frames)
{
return;
}

for (ULONG frame = 0; frame < 10; frame++)
{
ULONG64 imageBase;
const PRUNTIME_FUNCTION runtimeFunction = RtlLookupFunctionEntry(current.Rip, &imageBase, NULL);
const PRUNTIME_FUNCTION runtimeFunction = RtlLookupFunctionEntry(current.Rip, &imageBase, &historyTable);
if (!runtimeFunction)
{
break;
}

PVOID handlerData;
ULONG64 establisherFrame;
Expand All @@ -71,22 +73,17 @@ DECLSPEC_NOINLINE VOID HookFindRecord(VOID)
&nvContext);

if (!current.Rip)
{
break;
}

frames[frame] = current;

if (!(current.Rip >= g_KdTrap && current.Rip < g_KdTrap + 0x50))
{
continue;
}

/*
* 0: HookGuard!HookEntry+0x2d
* 1: nt!KeStallExecutionProcessor+0x9b
* 2: nt!KeFreezeExecution+0x110
* 3: nt!KdEnterDebugger+0x6d
* 4: nt!KdpReport+0x74
* 5: nt!KdpTrap+0x160
* 6: nt!KdTrap+0x2d
*/
const ULONG64 originalIrql = *(ULONG64*)(frames[2].Rsp + sizeof(ULONG64) * 1);

_enable();
Expand All @@ -95,22 +92,21 @@ DECLSPEC_NOINLINE VOID HookFindRecord(VOID)
const PEXCEPTION_RECORD exceptionRecord = *(PEXCEPTION_RECORD*)current.Rsp;
const PCONTEXT exceptionContext = *(PCONTEXT*)(current.Rsp + sizeof(ULONG64) * 10);

KdpPrint("Handling exception with code 0x%p, flags 0x%lx, RIP 0x%p, IRQL %lu\n", exceptionRecord->ExceptionCode, exceptionRecord->ExceptionFlags, exceptionContext->Rip, originalIrql);

if (exceptionRecord->ExceptionCode == STATUS_PRIVILEGED_INSTRUCTION)
{
HookHandlePrivilegedInstruction(exceptionRecord, exceptionContext);

if (exceptionRecord->ExceptionCode == STATUS_BREAKPOINT)
HookBreakpoint();
}

g_RtlDispatchException(exceptionRecord, exceptionContext);
break;
}

ExFreePool(frames);
}

DECLSPEC_NOINLINE ULONG64 HookEntry(ULONG64 arg1, ULONG64 arg2, ULONG64 arg3, ULONG64 arg4)
{
InterlockedIncrement64(&g_TotalCalls);
HookFindRecord();
return ((ULONG64(*)(ULONG64, ULONG64, ULONG64, ULONG64))(g_OriginalHandler))(arg1, arg2, arg3, arg4);
}
}