EfiGuardDxe: clear and restore CR0.WP when copying

This is intended to deal with the UEFI memory protection protocol (EFI_MEMORY_ATTRIBUTE_PROTOCOL) introduced in the UEFI 2.10 specification.

4 files changed, 38 insertions, 22 deletions

diff --git a/EfiGuardDxe/EfiGuardDxe.h b/EfiGuardDxe/EfiGuardDxe.h
index 0970d3b..249ed8c 100644
--- a/EfiGuardDxe/EfiGuardDxe.h
+++ b/EfiGuardDxe/EfiGuardDxe.h
@@ -49,6 +49,7 @@ extern BOOLEAN gEfiGoneVirtual;
 // Universal template bytes for a faux call inline hook (mov [e|r]ax, <addr>, push [e|r]ax, ret)
 //
 extern CONST UINT8 gHookTemplate[(sizeof(VOID*) / 4) + sizeof(VOID*) + 2];
+extern CONST UINTN gHookTemplateAddressOffset;
 
 
 //
diff --git a/EfiGuardDxe/PatchBootmgr.c b/EfiGuardDxe/PatchBootmgr.c
index 490d040..5730664 100644
--- a/EfiGuardDxe/PatchBootmgr.c
+++ b/EfiGuardDxe/PatchBootmgr.c
@@ -24,6 +24,11 @@ CONST UINT8 gHookTemplate[] =
 	0x50,											// push [e|r]ax
 	0xC3											// ret
 };
+#if defined(MDE_CPU_X64)
+CONST UINTN gHookTemplateAddressOffset = 2;
+#elif defined(MDE_CPU_IA32)
+CONST UINTN gHookTemplateAddressOffset = 1;
+#endif
 
 
 // Signature for [bootmgfw|bootmgr]!ImgArch[Efi]StartBootApplication
@@ -49,7 +54,7 @@ HookedBootManagerImgArchStartBootApplication(
 	)
 {
 	// Restore the original function bytes that we replaced with our hook
-	CopyMem(OriginalFunction, OriginalFunctionBytes, sizeof(gHookTemplate));
+	CopyWpMem(OriginalFunction, OriginalFunctionBytes, sizeof(gHookTemplate));
 
 	// Clear the screen and paint it, paint it bl... green
 	CONST INT32 OriginalAttribute = SetConsoleTextColour(EFI_GREEN, TRUE);
@@ -325,8 +330,8 @@ PatchBootManager(
 	CopyMem(BackupAddress, (VOID*)OriginalAddress, sizeof(gHookTemplate));
 
 	// Place faux call (push addr, ret) at the start of the function to transfer execution to our hook
-	CopyMem((VOID*)OriginalAddress, gHookTemplate, sizeof(gHookTemplate));
-	*(UINTN*)((UINT8*)OriginalAddress + 2) = (UINTN)HookAddress;
+	CopyWpMem((VOID*)OriginalAddress, gHookTemplate, sizeof(gHookTemplate));
+	CopyWpMem((UINT8*)OriginalAddress + gHookTemplateAddressOffset, (UINTN*)&HookAddress, sizeof(UINTN));
 
 	gBS->RestoreTPL(Tpl);
 
diff --git a/EfiGuardDxe/PatchNtoskrnl.c b/EfiGuardDxe/PatchNtoskrnl.c
index 1604f7a..fad6914 100644
--- a/EfiGuardDxe/PatchNtoskrnl.c
+++ b/EfiGuardDxe/PatchNtoskrnl.c
@@ -384,19 +384,19 @@ DisablePatchGuard(
 	// We have all the addresses we need; now do the actual patching.
 	CONST UINT32 Yes = 0xC301B0;	// mov al, 1, ret
 	CONST UINT32 No = 0xC3C033;		// xor eax, eax, ret
-	*((UINT32*)KeInitAmd64SpecificState) = No;
-	*((UINT32*)CcInitializeBcbProfiler) = Yes;
+	CopyWpMem(KeInitAmd64SpecificState, &No, sizeof(No));
+	CopyWpMem(CcInitializeBcbProfiler, &Yes, sizeof(Yes));
 	if (ExpLicenseWatchInitWorker != NULL)
-		*((UINT32*)ExpLicenseWatchInitWorker) = No;
+		CopyWpMem(ExpLicenseWatchInitWorker, &No, sizeof(No));
 	if (KiVerifyScopesExecute != NULL)
-		*(UINT32*)KiVerifyScopesExecute = No;
+		CopyWpMem(KiVerifyScopesExecute, &No, sizeof(No));
 	if (KiMcaDeferredRecoveryServiceCallers[0] != NULL && KiMcaDeferredRecoveryServiceCallers[1] != NULL)
 	{
-		*(UINT32*)KiMcaDeferredRecoveryServiceCallers[0] = No;
-		*(UINT32*)KiMcaDeferredRecoveryServiceCallers[1] = No;
+		CopyWpMem(KiMcaDeferredRecoveryServiceCallers[0], &No, sizeof(No));
+		CopyWpMem(KiMcaDeferredRecoveryServiceCallers[1], &No, sizeof(No));
 	}
 	if (KiSwInterruptPatternAddress != NULL)
-		SetMem(KiSwInterruptPatternAddress, sizeof(SigKiSwInterrupt), 0x90); // 11 x nop
+		SetWpMem(KiSwInterruptPatternAddress, sizeof(SigKiSwInterrupt), 0x90); // 11 x nop
 
 	// Print info
 	PRINT_KERNEL_PATCH_MSG(L"\r\n    Patched KeInitAmd64SpecificState [RVA: 0x%X].\r\n",
@@ -704,14 +704,20 @@ DisableDSE(
 	// We have all the addresses we need; now do the actual patching.
 	// SepInitializeCodeIntegrity is only patched when using the 'nuke option' DSE_DISABLE_AT_BOOT.
 	if (BypassType == DSE_DISABLE_AT_BOOT)
-		*((UINT16*)SepInitializeCodeIntegrityMovEcxAddress) = 0xC931;									// xor ecx, ecx
+	{
+		CONST UINT16 ZeroEcx = 0xC931;
+		CopyWpMem(SepInitializeCodeIntegrityMovEcxAddress, &ZeroEcx, sizeof(ZeroEcx));					// xor ecx, ecx
+	}
 
 	// SeValidateImageData *must* be patched on Windows Vista and 7 regardless of the DSE bypass method.
 	// On Windows >= 8, again require DSE_DISABLE_AT_BOOT to do anything as it is otherwise harmless.
 	if (BuildNumber < 9200)
-		*SeValidateImageDataJzAddress = 0xEB;															// jmp
+		SetWpMem(SeValidateImageDataJzAddress, sizeof(UINT8), 0xEB);									// jmp
 	else if (BypassType == DSE_DISABLE_AT_BOOT)
-		*(UINT32*)(SeValidateImageDataMovEaxAddress + 1 /*skip existing mov opcode*/) = 0x0;	// mov eax, 0
+	{
+		CONST UINT32 Zero = 0;
+		CopyWpMem(SeValidateImageDataMovEaxAddress + 1 /*skip existing mov*/, &Zero, sizeof(Zero));		// mov eax, 0
+	}
 
 	if (BuildNumber >= 16299 && BypassType == DSE_DISABLE_AT_BOOT)
 	{
diff --git a/EfiGuardDxe/PatchWinload.c b/EfiGuardDxe/PatchWinload.c
index edf15ad..baa28d7 100644
--- a/EfiGuardDxe/PatchWinload.c
+++ b/EfiGuardDxe/PatchWinload.c
@@ -128,7 +128,7 @@ HookedOslFwpKernelSetupPhase1(
 	)
 {
 	// Restore the original function bytes that we replaced with our hook
-	CopyMem((VOID*)gOriginalOslFwpKernelSetupPhase1, gOslFwpKernelSetupPhase1Backup, sizeof(gOslFwpKernelSetupPhase1Backup));
+	CopyWpMem((VOID*)gOriginalOslFwpKernelSetupPhase1, gOslFwpKernelSetupPhase1Backup, sizeof(gHookTemplate));
 
 	UINT8* LoadOrderListHeadAddress = (UINT8*)&LoaderBlock->LoadOrderListHead;
 	if (gKernelPatchInfo.BuildNumber < 7600)
@@ -238,7 +238,7 @@ PatchImgpValidateImageHash(
 	}
 
 	// Backtrack to function start
-	CONST UINT8* ImgpValidateImageHash = BacktrackToFunctionStart(ImageBase, NtHeaders, AndMinusFortyOneAddress);
+	UINT8* ImgpValidateImageHash = BacktrackToFunctionStart(ImageBase, NtHeaders, AndMinusFortyOneAddress);
 	if (ImgpValidateImageHash == NULL)
 	{
 		Print(L"    Failed to find %S!ImgpValidateImageHash%S.\r\n",
@@ -247,7 +247,8 @@ PatchImgpValidateImageHash(
 	}
 
 	// Apply the patch
-	*((UINT32*)ImgpValidateImageHash) = 0xC3C033; // xor eax, eax, ret
+	CONST UINT32 Ok = 0xC3C033; // xor eax, eax, ret
+	CopyWpMem(ImgpValidateImageHash, &Ok, sizeof(Ok));
 
 	// Print info
 	Print(L"    Patched %S!ImgpValidateImageHash [RVA: 0x%X].\r\n",
@@ -375,7 +376,7 @@ PatchImgpFilterValidationFailure(
 	}
 
 	// Backtrack to function start
-	CONST UINT8* ImgpFilterValidationFailure = BacktrackToFunctionStart(ImageBase, NtHeaders, LeaIntegrityFailureAddress);
+	UINT8* ImgpFilterValidationFailure = BacktrackToFunctionStart(ImageBase, NtHeaders, LeaIntegrityFailureAddress);
 	if (ImgpFilterValidationFailure == NULL)
 	{
 		Print(L"    Failed to find %S!ImgpFilterValidationFailure%S.\r\n",
@@ -384,7 +385,8 @@ PatchImgpFilterValidationFailure(
 	}
 
 	// Apply the patch
-	*((UINT32*)ImgpFilterValidationFailure) = 0xC3C033; // xor eax, eax, ret
+	CONST UINT32 Ok = 0xC3C033; // xor eax, eax, ret
+	CopyWpMem(ImgpFilterValidationFailure, &Ok, sizeof(Ok));
 
 	// Print info
 	Print(L"    Patched %S!ImgpFilterValidationFailure [RVA: 0x%X].\r\n\r\n",
@@ -679,16 +681,18 @@ PatchWinload(
 		goto Exit;
 	}
 
-	Print(L"HookedOslFwpKernelSetupPhase1 at 0x%p.\r\n", (VOID*)&HookedOslFwpKernelSetupPhase1);
+	CONST UINTN HookedOslFwpKernelSetupPhase1Address = (UINTN)&HookedOslFwpKernelSetupPhase1;
+	Print(L"HookedOslFwpKernelSetupPhase1 at 0x%p.\r\n", (VOID*)HookedOslFwpKernelSetupPhase1Address);
 
 	CONST EFI_TPL Tpl = gBS->RaiseTPL(TPL_HIGH_LEVEL); // Note: implies cli
 
 	// Backup original function prologue
-	CopyMem(gOslFwpKernelSetupPhase1Backup, (VOID*)gOriginalOslFwpKernelSetupPhase1, sizeof(gOslFwpKernelSetupPhase1Backup));
+	CopyMem(gOslFwpKernelSetupPhase1Backup, (VOID*)gOriginalOslFwpKernelSetupPhase1, sizeof(gHookTemplate));
 
 	// Place faux call (push addr, ret) at the start of the function to transfer execution to our hook
-	CopyMem((VOID*)gOriginalOslFwpKernelSetupPhase1, gHookTemplate, sizeof(gHookTemplate));
-	*(UINTN*)((UINT8*)gOriginalOslFwpKernelSetupPhase1 + 2) = (UINTN)&HookedOslFwpKernelSetupPhase1;
+	CopyWpMem((VOID*)gOriginalOslFwpKernelSetupPhase1, gHookTemplate, sizeof(gHookTemplate));
+	CopyWpMem((UINT8*)gOriginalOslFwpKernelSetupPhase1 + gHookTemplateAddressOffset,
+		(UINTN*)&HookedOslFwpKernelSetupPhase1Address, sizeof(HookedOslFwpKernelSetupPhase1Address));
 
 	gBS->RestoreTPL(Tpl);