Code_Virtualizer/CodeVirtualizer/XorInstructions.cpp

#include "XorInstructions.h"


BOOL ObfEmitPushfqInst(PNATIVE_CODE_BLOCK Block)
{
	PNATIVE_CODE_LINK Link = new NATIVE_CODE_LINK;
	Link->Flags = CODE_FLAG_IS_INST;
	Link->RawData = new UCHAR[1];
	*(PUCHAR)(Link->RawData) = 0x9C;
	Link->RawDataSize = 1;
	XED_ERROR_ENUM DecodeError = XedDecode(&Link->XedInst, Link->RawData, 1);
	if (DecodeError != XED_ERROR_NONE)
	{
		printf("Pushfq decode failed with error %s\n", XedErrorEnumToString(DecodeError));
		delete Link;
		return FALSE;
	}
	Link->Block = Block;
	Link->Prev = Block->End;
	Block->End->Next = Link;
	Block->End = Link;
	return TRUE;
}

BOOL ObfEmitPopfqInst(PNATIVE_CODE_BLOCK Block)
{
	PNATIVE_CODE_LINK Link = new NATIVE_CODE_LINK;
	Link->Flags = CODE_FLAG_IS_INST;
	Link->RawData = new UCHAR[1];
	*(PUCHAR)(Link->RawData) = 0x9D;
	Link->RawDataSize = 1;
	XED_ERROR_ENUM DecodeError = XedDecode(&Link->XedInst, Link->RawData, 1);
	if (DecodeError != XED_ERROR_NONE)
	{
		printf("Popfq decode failed with error %s\n", XedErrorEnumToString(DecodeError));
		delete Link;
		return FALSE;
	}
	Link->Block = Block;
	Link->Prev = Block->End;
	Block->End->Next = Link;
	Block->End = Link;
	return TRUE;
}

BOOL ObfEmitRipRelativeXorD(PNATIVE_CODE_BLOCK Block, INT32 RipDelta, ULONG Value)
{
	UCHAR Bytes[] = { 0x81, 0x35, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };

	PNATIVE_CODE_LINK Link = new NATIVE_CODE_LINK;
	Link->Flags = CODE_FLAG_IS_INST;
	Link->RawData = new UCHAR[DWORD_XOR_INST_LENGTH];
	Link->RawDataSize = DWORD_XOR_INST_LENGTH;
	memcpy(Link->RawData, Bytes, DWORD_XOR_INST_LENGTH);

	*(PINT32)&Link->RawData[DWORD_XOR_INST_RIP_OFFSET] = RipDelta;
	*(PULONG)&Link->RawData[DWORD_XOR_INST_XOR_OFFSET] = Value;

	XED_ERROR_ENUM DecodeError = XedDecode(&Link->XedInst, Link->RawData, Link->RawDataSize);
	if (DecodeError != XED_ERROR_NONE)
	{
		printf("XedDecode failed with error %s\n", XedErrorEnumToString(DecodeError));
		delete Link;
		return FALSE;
	}
	Link->Block = Block;
	Link->Prev = Block->End;
	Block->End->Next = Link;
	Block->End = Link;
	return TRUE;
}

BOOL ObfEmitRipRelativeXorW(PNATIVE_CODE_BLOCK Block, INT32 RipDelta, ULONG Value)
{
	UCHAR Bytes[] = { 0x66, 0x81, 0x35, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };

	PNATIVE_CODE_LINK Link = new NATIVE_CODE_LINK;
	Link->Flags = CODE_FLAG_IS_INST;
	Link->RawData = new UCHAR[WORD_XOR_INST_LENGTH];
	Link->RawDataSize = WORD_XOR_INST_LENGTH;
	memcpy(Link->RawData, Bytes, WORD_XOR_INST_LENGTH);

	*(PINT32)&Link->RawData[WORD_XOR_INST_RIP_OFFSET] = RipDelta;
	*(PUSHORT)&Link->RawData[WORD_XOR_INST_XOR_OFFSET] = (USHORT)Value;

	XED_ERROR_ENUM DecodeError = XedDecode(&Link->XedInst, Link->RawData, Link->RawDataSize);
	if (DecodeError != XED_ERROR_NONE)
	{
		printf("XedDecode failed with error %s\n", XedErrorEnumToString(DecodeError));
		delete Link;
		return FALSE;
	}
	Link->Block = Block;
	Link->Prev = Block->End;
	Block->End->Next = Link;
	Block->End = Link;
	return TRUE;
}

BOOL ObfEmitRipRelativeXorB(PNATIVE_CODE_BLOCK Block, INT32 RipDelta, ULONG Value)
{
	UCHAR Bytes[] = { 0x80, 0x35, 0x00, 0x00, 0x00, 0x00, 0x00 };

	PNATIVE_CODE_LINK Link = new NATIVE_CODE_LINK;
	Link->Flags = CODE_FLAG_IS_INST;
	Link->RawData = new UCHAR[BYTE_XOR_INST_LENGTH];
	Link->RawDataSize = BYTE_XOR_INST_LENGTH;
	memcpy(Link->RawData, Bytes, BYTE_XOR_INST_LENGTH);

	*(PINT32)&Link->RawData[BYTE_XOR_INST_RIP_OFFSET] = RipDelta;
	*(PUCHAR)&Link->RawData[BYTE_XOR_INST_XOR_OFFSET] = (UCHAR)Value;

	XED_ERROR_ENUM DecodeError = XedDecode(&Link->XedInst, Link->RawData, Link->RawDataSize);
	if (DecodeError != XED_ERROR_NONE)
	{
		printf("XedDecode failed with error %s\n", XedErrorEnumToString(DecodeError));
		delete Link;
		return FALSE;
	}
	Link->Block = Block;
	Link->Prev = Block->End;
	Block->End->Next = Link;
	Block->End = Link;
	return TRUE;
}

PNATIVE_CODE_BLOCK ObfEmitPreXorForInst(PNATIVE_CODE_LINK Link, PXOR_INST_DATA XorData, BOOL SaveFlags)
{
	ULONG FourByte = Link->RawDataSize / 4;
	ULONG TwoByte = (Link->RawDataSize - (FourByte * 4)) / 2;
	ULONG OneByte = (Link->RawDataSize - (FourByte * 4) - (TwoByte * 2));

	PNATIVE_CODE_BLOCK Block = new NATIVE_CODE_BLOCK;

	Block->Start = Block->End = new NATIVE_CODE_LINK;

	if (SaveFlags && !ObfEmitPushfqInst(Block))
	{
		NcDelete(Block);
		delete Block;
		return NULL;
	}
		
	ULONG Count = FourByte;
	while (Count)
	{
		//Account for remaining XORs
		INT32 RipDelta = (((Count - 1) * DWORD_XOR_INST_LENGTH) + (TwoByte * WORD_XOR_INST_LENGTH) + (OneByte * BYTE_XOR_INST_LENGTH));
		//Account for POPFQ
		if (SaveFlags)
			RipDelta += 1;
		//Account for already XORd instructions
		RipDelta += ((FourByte - Count) * 4);
		//Add the actual instruction
		if (!ObfEmitRipRelativeXorD(Block, RipDelta, XorData->Data[FourByte-Count]))
		{
			NcDelete(Block);
			delete Block;
			return NULL;
		}
		--Count;
	}

	if (TwoByte)
	{
		INT32 RipDelta = (OneByte * BYTE_XOR_INST_LENGTH);
		if (SaveFlags)
			RipDelta += 1;
		RipDelta += (FourByte * 4);
		if (!ObfEmitRipRelativeXorW(Block, RipDelta, XorData->Data[3]))
		{
			NcDelete(Block);
			delete Block;
			return NULL;
		}
	}

	if (OneByte)
	{
		INT32 RipDelta = 0;
		if (SaveFlags)
			RipDelta += 1;
		RipDelta += (FourByte * 4) + (TwoByte * 2);
		if (!ObfEmitRipRelativeXorB(Block, RipDelta, XorData->Data[4]))
		{
			NcDelete(Block);
			delete Block;
			return NULL;
		}
	}

	if (SaveFlags && !ObfEmitPopfqInst(Block))
	{
		NcDelete(Block);
		delete Block;
		return NULL;
	}

	PNATIVE_CODE_LINK StartLink = Block->Start;
	Block->Start = Block->Start->Next;
	if (Block->Start)
		Block->Start->Prev = NULL;
	delete StartLink;

	return Block;
}

PNATIVE_CODE_BLOCK ObfEmitPostXorForInst(PNATIVE_CODE_LINK Link, PXOR_INST_DATA XorData, BOOL SaveFlags)
{
	ULONG FourByte = Link->RawDataSize / 4;
	ULONG TwoByte = (Link->RawDataSize - (FourByte * 4)) / 2;
	ULONG OneByte = (Link->RawDataSize - (FourByte * 4) - (TwoByte * 2));

	PNATIVE_CODE_BLOCK Block = new NATIVE_CODE_BLOCK;

	Block->Start = Block->End = new NATIVE_CODE_LINK;

	if (SaveFlags && !ObfEmitPushfqInst(Block))
	{
		NcDelete(Block);
		delete Block;
		return NULL;
	}

	ULONG Count = FourByte;
	while (Count)
	{

		INT32 RipDelta = Link->RawDataSize - ((FourByte - Count) * 4);
		if (SaveFlags)
			RipDelta += 1;

		RipDelta += (FourByte - (Count - 1)) * DWORD_XOR_INST_LENGTH;

		RipDelta *= (-1);

		if (!ObfEmitRipRelativeXorD(Block, RipDelta, XorData->Data[FourByte - Count]))
		{
			NcDelete(Block);
			delete Block;
			return NULL;
		}

		--Count;
	}

	if (TwoByte)
	{
		INT32 RipDelta = Link->RawDataSize - (FourByte * 4);
		if (SaveFlags)
			RipDelta += 1;

		RipDelta += (FourByte * DWORD_XOR_INST_LENGTH);

		RipDelta += WORD_XOR_INST_LENGTH;

		RipDelta *= (-1);

		if (!ObfEmitRipRelativeXorW(Block, RipDelta, XorData->Data[3]))
		{
			NcDelete(Block);
			delete Block;
			return NULL;
		}
	}

	if (OneByte)
	{
		INT32 RipDelta = Link->RawDataSize - (FourByte * 4) - (TwoByte * 2);
		if (SaveFlags)
			RipDelta += 1;

		RipDelta += (FourByte * DWORD_XOR_INST_LENGTH);

		RipDelta += WORD_XOR_INST_LENGTH;

		RipDelta += BYTE_XOR_INST_LENGTH;

		RipDelta *= (-1);

		if (!ObfEmitRipRelativeXorB(Block, RipDelta, XorData->Data[4]))
		{
			NcDelete(Block);
			delete Block;
			return NULL;
		}
	}

	if (SaveFlags && !ObfEmitPopfqInst(Block))
	{
		NcDelete(Block);
		delete Block;
		return NULL;
	}

	PNATIVE_CODE_LINK StartLink = Block->Start;
	Block->Start = Block->Start->Next;
	if (Block->Start)
		Block->Start->Prev = NULL;
	delete StartLink;

	return Block;
}