/*
Copyright (C) 2011-2012 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 dot10.DotNet;
using dot10.DotNet.Emit;
using de4dot.blocks;
using de4dot.blocks.cflow;
namespace de4dot.code.deobfuscators.DeepSea {
class ArrayBlockDeobfuscator : BlockDeobfuscator {
ArrayBlockState arrayBlockState;
Dictionary localToInfo = new Dictionary();
DsConstantsReader constantsReader;
public ArrayBlockDeobfuscator(ArrayBlockState arrayBlockState) {
this.arrayBlockState = arrayBlockState;
}
public override void deobfuscateBegin(Blocks blocks) {
base.deobfuscateBegin(blocks);
initLocalToInfo();
}
void initLocalToInfo() {
localToInfo.Clear();
foreach (var block in blocks.MethodBlocks.getAllBlocks()) {
var instrs = block.Instructions;
for (int i = 0; i < instrs.Count - 1; i++) {
var ldsfld = instrs[i];
if (ldsfld.OpCode.Code != Code.Ldsfld)
continue;
var stloc = instrs[i + 1];
if (!stloc.isStloc())
continue;
var info = arrayBlockState.getFieldInfo((IField)ldsfld.Operand);
if (info == null)
continue;
var local = stloc.Instruction.GetLocal(blocks.Locals);
if (local == null)
continue;
localToInfo[local] = info;
}
}
}
protected override bool deobfuscate(Block block) {
bool changed = false;
constantsReader = null;
var instrs = block.Instructions;
for (int i = 0; i < instrs.Count; i++) {
bool ch = deobfuscate1(block, i);
if (ch) {
changed = true;
continue;
}
ch = deobfuscate2(block, i);
if (ch) {
changed = true;
continue;
}
ch = deobfuscate3(block, i);
if (ch) {
changed = true;
continue;
}
}
return changed;
}
static bool IsLdelem(ArrayBlockState.FieldInfo info, Code code) {
switch (info.elementType) {
case ElementType.Boolean:
case ElementType.I1:
case ElementType.U1:
return code == Code.Ldelem_I1 || code == Code.Ldelem_U1;
case ElementType.Char:
case ElementType.I2:
case ElementType.U2:
return code == Code.Ldelem_I2 || code == Code.Ldelem_U2;
case ElementType.I4:
case ElementType.U4:
return code == Code.Ldelem_I4 || code == Code.Ldelem_U4;
default:
return false;
}
}
static bool IsStelem(ArrayBlockState.FieldInfo info, Code code) {
switch (info.elementType) {
case ElementType.Boolean:
case ElementType.I1:
case ElementType.U1:
return code == Code.Stelem_I1;
case ElementType.Char:
case ElementType.I2:
case ElementType.U2:
return code == Code.Stelem_I2;
case ElementType.I4:
case ElementType.U4:
return code == Code.Stelem_I4;
default:
return false;
}
}
bool deobfuscate1(Block block, int i) {
var instrs = block.Instructions;
if (i >= instrs.Count - 2)
return false;
var ldloc = instrs[i];
if (!ldloc.isLdloc())
return false;
var local = ldloc.Instruction.GetLocal(blocks.Locals);
if (local == null)
return false;
ArrayBlockState.FieldInfo info;
if (!localToInfo.TryGetValue(local, out info))
return false;
var ldci4 = instrs[i + 1];
if (!ldci4.isLdcI4())
return false;
var ldelem = instrs[i + 2];
if (!IsLdelem(info, ldelem.OpCode.Code))
return false;
block.remove(i, 3 - 1);
instrs[i] = new Instr(Instruction.CreateLdcI4((int)info.readArrayElement(ldci4.getLdcI4Value())));
return true;
}
bool deobfuscate2(Block block, int i) {
var instrs = block.Instructions;
if (i >= instrs.Count - 2)
return false;
var ldsfld = instrs[i];
if (ldsfld.OpCode.Code != Code.Ldsfld)
return false;
var info = arrayBlockState.getFieldInfo(ldsfld.Operand as IField);
if (info == null)
return false;
var ldci4 = instrs[i + 1];
if (!ldci4.isLdcI4())
return false;
var ldelem = instrs[i + 2];
if (!IsLdelem(info, ldelem.OpCode.Code))
return false;
block.remove(i, 3 - 1);
instrs[i] = new Instr(Instruction.CreateLdcI4((int)info.readArrayElement(ldci4.getLdcI4Value())));
return true;
}
bool deobfuscate3(Block block, int i) {
var instrs = block.Instructions;
if (i + 1 >= instrs.Count)
return false;
int start = i;
var ldsfld = instrs[i];
if (ldsfld.OpCode.Code != Code.Ldsfld)
return false;
var info = arrayBlockState.getFieldInfo(ldsfld.Operand as IField);
if (info == null)
return false;
if (!instrs[i + 1].isLdcI4())
return false;
var constants = getConstantsReader(block);
int value;
i += 2;
if (!constants.getInt32(ref i, out value))
return false;
if (i >= instrs.Count)
return false;
var stelem = instrs[i];
if (!IsStelem(info, stelem.OpCode.Code))
return false;
block.remove(start, i - start + 1);
return true;
}
DsConstantsReader getConstantsReader(Block block) {
if (constantsReader != null)
return constantsReader;
return constantsReader = new DsConstantsReader(block.Instructions);
}
}
}