/*
Copyright (C) 2011-2013 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;
using System.Collections.Generic;
using dnlib.DotNet;
using dnlib.DotNet.Emit;
using de4dot.blocks;
namespace de4dot.blocks.cflow {
// Very simple constants folder which is all that's needed at the moment
class ConstantsFolder : BlockDeobfuscator {
InstructionEmulator instructionEmulator = new InstructionEmulator();
IList args;
protected override void Initialize(List allBlocks) {
base.Initialize(allBlocks);
args = blocks.Method.Parameters;
}
protected override bool Deobfuscate(Block block) {
bool modified = false;
instructionEmulator.Initialize(blocks);
var instrs = block.Instructions;
for (int i = 0; i < instrs.Count; i++) {
var instr = instrs[i];
switch (instr.OpCode.Code) {
case Code.Ldarg:
case Code.Ldarg_0:
case Code.Ldarg_1:
case Code.Ldarg_2:
case Code.Ldarg_3:
case Code.Ldarg_S:
modified |= FixLoadInstruction(block, i, instructionEmulator.GetArg(instr.Instruction.GetParameter(args)));
break;
case Code.Ldloc:
case Code.Ldloc_0:
case Code.Ldloc_1:
case Code.Ldloc_2:
case Code.Ldloc_3:
case Code.Ldloc_S:
modified |= FixLoadInstruction(block, i, instructionEmulator.GetLocal(instr.Instruction.GetLocal(blocks.Locals)));
break;
case Code.Ldarga:
case Code.Ldarga_S:
instructionEmulator.MakeArgUnknown((Parameter)instr.Operand);
break;
case Code.Ldloca:
case Code.Ldloca_S:
instructionEmulator.MakeLocalUnknown((Local)instr.Operand);
break;
}
try {
instructionEmulator.Emulate(instr.Instruction);
}
catch (NullReferenceException) {
// Here if eg. invalid metadata token in a call instruction (operand is null)
break;
}
}
return modified;
}
bool FixLoadInstruction(Block block, int index, Value value) {
if (value.IsInt32()) {
var intValue = (Int32Value)value;
if (!intValue.AllBitsValid())
return false;
block.Instructions[index] = new Instr(Instruction.CreateLdcI4(intValue.Value));
return true;
}
else if (value.IsInt64()) {
var intValue = (Int64Value)value;
if (!intValue.AllBitsValid())
return false;
block.Instructions[index] = new Instr(OpCodes.Ldc_I8.ToInstruction(intValue.Value));
return true;
}
return false;
}
}
}