188 lines
4.5 KiB
C++
188 lines
4.5 KiB
C++
/*++
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Copyright (c) 2001 Microsoft Corporation
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Module Name:
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DominantSpecies.cpp
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Abstract:
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See Force21 shim - almost exactly the same problem.
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DominantSpecies contains an invalid check code that looks like the following:
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mov esi,A
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mov eax,B
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sub eax,esi
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cmp eax,ebp
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jle @@Loc
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mov eax,ebp
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@@Loc:
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In a particular case: B=-1 and A<0x80000000 this jump will be incorrectly
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taken. The reason this works on Win9x is that A>0x80000000 because it's a
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memory mapped file. On NT, no user mode address can normally be >2GB.
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This shim patches the app with a 'cli' instruction so that it can perform
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some logic when the exception gets hit. This is admittedly slow.
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Note we didn't use the in memory patching facility of the shim because we
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still needed logic. It didn't make sense to split the shim from the patch.
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Also, we can't have a general shim which makes all memory addresses high and
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catches the fallout, because game performance suffers too much.
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Notes:
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This is an app specific shim.
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History:
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06/30/2001 linstev Created
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--*/
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#include "precomp.h"
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IMPLEMENT_SHIM_BEGIN(DominantSpecies)
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#include "ShimHookMacro.h"
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APIHOOK_ENUM_BEGIN
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APIHOOK_ENUM_END
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/*++
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In memory patch the executable with a cli instruction. This patch works
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for both the release version and a patch.
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--*/
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VOID
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ExecutePatch()
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{
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BYTE bPatchMatch[] = {
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0x2b, 0xc6, 0x3b, 0xc5, 0x7c, 0x02, 0x8b, 0xc5, 0x85, 0xc0 };
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LPBYTE pPatchAddress[] = {
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(LPBYTE)0x53f543, // the shipping version
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(LPBYTE)0x000000}; // placeholder for a vendor patch in case they get it wrong again
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BYTE bPatch = 0xFA; // cli - to cause an exception
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//
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// Run through the patches and see which one matches
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//
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for (UINT j=0; j<sizeof(pPatchAddress)/sizeof(LPBYTE); j++)
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{
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LPBYTE pb = pPatchAddress[j];
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// Make sure it's an OK address.
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if (!IsBadReadPtr(pb, sizeof(bPatchMatch)))
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{
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// Check the bytes match
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for (UINT i=0; i < sizeof(bPatchMatch); i++)
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{
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if (*pb != bPatchMatch[i])
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{
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break;
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}
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pb++;
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}
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// In memory patch
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if (i == sizeof(bPatchMatch))
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{
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DWORD dwOldProtect;
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if (VirtualProtect(
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(PVOID)pPatchAddress[j],
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1,
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PAGE_READWRITE,
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&dwOldProtect))
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{
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*pPatchAddress[j] = bPatch;
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LOGN(
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eDbgLevelError,
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"Successfully patched\n");
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return;
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}
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}
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}
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}
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}
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/*++
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Handle the cli in such a way that the correct logic is performed.
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--*/
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LONG
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ExceptionFilter(
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struct _EXCEPTION_POINTERS *ExceptionInfo
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)
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{
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CONTEXT *lpContext = ExceptionInfo->ContextRecord;
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if (ExceptionInfo->ExceptionRecord->ExceptionCode == EXCEPTION_PRIV_INSTRUCTION)
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{
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// Looks like we've hit our cli instruction
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if ((LONG)lpContext->Eax < 0) // Boundary condition, EDI<0
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{
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// Jump past the invalid check
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lpContext->Eip = lpContext->Eip + 6;
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}
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else
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{
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// Replace the 'sub edi,eax' and continue
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lpContext->Eax = lpContext->Eax - lpContext->Esi;
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lpContext->Eip = lpContext->Eip + 2;
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}
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return EXCEPTION_CONTINUE_EXECUTION;
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}
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return EXCEPTION_CONTINUE_SEARCH;
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}
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/*++
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Register hooked functions
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--*/
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BOOL
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NOTIFY_FUNCTION(
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DWORD fdwReason)
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{
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if (fdwReason == DLL_PROCESS_ATTACH)
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{
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ExecutePatch();
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// Try to find new exception handler
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_pfn_RtlAddVectoredExceptionHandler pfnExcept;
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pfnExcept = (_pfn_RtlAddVectoredExceptionHandler)
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GetProcAddress(
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GetModuleHandle(L"NTDLL.DLL"),
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"RtlAddVectoredExceptionHandler");
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if (pfnExcept)
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{
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(_pfn_RtlAddVectoredExceptionHandler) pfnExcept(
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0,
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(PVOID)ExceptionFilter);
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}
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}
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return TRUE;
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}
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HOOK_BEGIN
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CALL_NOTIFY_FUNCTION
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HOOK_END
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IMPLEMENT_SHIM_END
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