/*
Copyright (C) 2011-2015 de4dot@gmail.com
This file is part of de4dot.
de4dot is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
de4dot is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with de4dot. If not, see .
*/
using System.Collections.Generic;
using dnlib.DotNet.Emit;
using de4dot.blocks;
using de4dot.blocks.cflow;
namespace de4dot.code.deobfuscators.Confuser {
class ConstantsFolder : BlockDeobfuscator {
protected override bool Deobfuscate(Block block) {
bool modified = false;
var instrs = block.Instructions;
var constantsReader = CreateConstantsReader(instrs);
for (int i = 0; i < instrs.Count; i++) {
int index = 0;
Instruction newInstr = null;
var instr = instrs[i];
if (constantsReader.IsLoadConstantInt32(instr.Instruction)) {
index = i;
int val;
if (!constantsReader.GetInt32(ref index, out val))
continue;
newInstr = Instruction.CreateLdcI4(val);
}
else if (constantsReader.IsLoadConstantInt64(instr.Instruction)) {
index = i;
long val;
if (!constantsReader.GetInt64(ref index, out val))
continue;
newInstr = Instruction.Create(OpCodes.Ldc_I8, val);
}
else if (constantsReader.IsLoadConstantDouble(instr.Instruction)) {
index = i;
double val;
if (!constantsReader.GetDouble(ref index, out val))
continue;
newInstr = Instruction.Create(OpCodes.Ldc_R8, val);
}
if (newInstr != null && index - i > 1) {
block.Insert(index++, Instruction.Create(OpCodes.Pop));
block.Insert(index++, newInstr);
i = index - 1;
constantsReader = CreateConstantsReader(instrs);
modified = true;
continue;
}
// Convert ldc.r4/r8 followed by conv to the appropriate ldc.i4/i8 instr
if (i + 1 < instrs.Count && (instr.OpCode.Code == Code.Ldc_R4 || instr.OpCode.Code == Code.Ldc_R8)) {
var conv = instrs[i + 1];
int vali32 = instr.OpCode.Code == Code.Ldc_R4 ? (int)(float)instr.Operand : (int)(double)instr.Operand;
long vali64 = instr.OpCode.Code == Code.Ldc_R4 ? (long)(float)instr.Operand : (long)(double)instr.Operand;
uint valu32 = instr.OpCode.Code == Code.Ldc_R4 ? (uint)(float)instr.Operand : (uint)(double)instr.Operand;
ulong valu64 = instr.OpCode.Code == Code.Ldc_R4 ? (ulong)(float)instr.Operand : (ulong)(double)instr.Operand;
switch (conv.OpCode.Code) {
case Code.Conv_I1:
newInstr = Instruction.CreateLdcI4(instr.OpCode.Code == Code.Ldc_R4 ? (sbyte)(float)instr.Operand : (sbyte)(double)instr.Operand);
break;
case Code.Conv_U1:
newInstr = Instruction.CreateLdcI4(instr.OpCode.Code == Code.Ldc_R4 ? (byte)(float)instr.Operand : (byte)(double)instr.Operand);
break;
case Code.Conv_I2:
newInstr = Instruction.CreateLdcI4(instr.OpCode.Code == Code.Ldc_R4 ? (short)(float)instr.Operand : (short)(double)instr.Operand);
break;
case Code.Conv_U2:
newInstr = Instruction.CreateLdcI4(instr.OpCode.Code == Code.Ldc_R4 ? (ushort)(float)instr.Operand : (ushort)(double)instr.Operand);
break;
case Code.Conv_I4:
newInstr = Instruction.CreateLdcI4(instr.OpCode.Code == Code.Ldc_R4 ? (int)(float)instr.Operand : (int)(double)instr.Operand);
break;
case Code.Conv_U4:
newInstr = Instruction.CreateLdcI4(instr.OpCode.Code == Code.Ldc_R4 ? (int)(uint)(float)instr.Operand : (int)(uint)(double)instr.Operand);
break;
case Code.Conv_I8:
newInstr = Instruction.Create(OpCodes.Ldc_I8, instr.OpCode.Code == Code.Ldc_R4 ? (long)(float)instr.Operand : (long)(double)instr.Operand);
break;
case Code.Conv_U8:
newInstr = Instruction.Create(OpCodes.Ldc_I8, instr.OpCode.Code == Code.Ldc_R4 ? (ulong)(float)instr.Operand : (ulong)(double)instr.Operand);
break;
default:
newInstr = null;
break;
}
if (newInstr != null) {
block.Replace(i, 2, newInstr);
constantsReader = CreateConstantsReader(instrs);
modified = true;
continue;
}
}
}
return modified;
}
static ConstantsReader CreateConstantsReader(IList instrs) {
return new ConstantsReader(instrs, false);
}
}
}