/*
Copyright (C) 2011 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 Mono.Cecil;
using Mono.Cecil.Cil;
namespace de4dot.blocks.cflow {
class BlockControlFlowDeobfuscator {
Block block;
InstructionEmulator instructionEmulator = new InstructionEmulator();
public void init(Block block, IList args, IList locals) {
this.block = block;
instructionEmulator.init(false, args, locals);
}
// Returns true if code was updated, false otherwise
public bool deobfuscate() {
var instructions = block.Instructions;
if (instructions.Count == 0)
return false;
for (int i = 0; i < instructions.Count - 1; i++) {
instructionEmulator.emulate(instructions[i].Instruction);
}
switch (block.LastInstr.OpCode.Code) {
case Code.Beq:
case Code.Beq_S: return emulate_Beq();
case Code.Bge:
case Code.Bge_S: return emulate_Bge();
case Code.Bge_Un:
case Code.Bge_Un_S: return emulate_Bge_Un();
case Code.Bgt:
case Code.Bgt_S: return emulate_Bgt();
case Code.Bgt_Un:
case Code.Bgt_Un_S: return emulate_Bgt_Un();
case Code.Ble:
case Code.Ble_S: return emulate_Ble();
case Code.Ble_Un:
case Code.Ble_Un_S: return emulate_Ble_Un();
case Code.Blt:
case Code.Blt_S: return emulate_Blt();
case Code.Blt_Un:
case Code.Blt_Un_S: return emulate_Blt_Un();
case Code.Bne_Un:
case Code.Bne_Un_S: return emulate_Bne_Un();
case Code.Brfalse:
case Code.Brfalse_S:return emulate_Brfalse();
case Code.Brtrue:
case Code.Brtrue_S: return emulate_Brtrue();
default:
return false;
}
}
bool emulateBranch(int stackArgs, Bool3 cond) {
if (cond == Bool3.Unknown)
return false;
return emulateBranch(stackArgs, cond == Bool3.True);
}
bool emulateBranch(int stackArgs, bool isTaken) {
// Pop the arguments to the bcc instruction. The dead code remover will get rid of the
// pop and any pushed arguments. Insert the pops just before the bcc instr.
for (int i = 0; i < stackArgs; i++)
block.insert(block.Instructions.Count - 1, Instruction.Create(OpCodes.Pop));
block.replaceBccWithBranch(isTaken);
return true;
}
bool emulate_Beq() {
var val2 = instructionEmulator.pop();
var val1 = instructionEmulator.pop();
if (val1.valueType == ValueType.Int32 && val2.valueType == ValueType.Int32)
return emulateBranch(2, Int32Value.compareEq((Int32Value)val1, (Int32Value)val2));
else if (val1.valueType == ValueType.Int64 && val2.valueType == ValueType.Int64)
return emulateBranch(2, Int64Value.compareEq((Int64Value)val1, (Int64Value)val2));
else if (val1.valueType == ValueType.Null && val2.valueType == ValueType.Null)
return emulateBranch(2, true);
else
return false;
}
bool emulate_Bne_Un() {
var val2 = instructionEmulator.pop();
var val1 = instructionEmulator.pop();
if (val1.valueType == ValueType.Int32 && val2.valueType == ValueType.Int32)
return emulateBranch(2, Int32Value.compareNeq((Int32Value)val1, (Int32Value)val2));
else if (val1.valueType == ValueType.Int64 && val2.valueType == ValueType.Int64)
return emulateBranch(2, Int64Value.compareNeq((Int64Value)val1, (Int64Value)val2));
else if (val1.valueType == ValueType.Null && val2.valueType == ValueType.Null)
return emulateBranch(2, false);
else
return false;
}
bool emulate_Bge() {
var val2 = instructionEmulator.pop();
var val1 = instructionEmulator.pop();
if (val1.valueType == ValueType.Int32 && val2.valueType == ValueType.Int32)
return emulateBranch(2, Int32Value.compareGe((Int32Value)val1, (Int32Value)val2));
else if (val1.valueType == ValueType.Int64 && val2.valueType == ValueType.Int64)
return emulateBranch(2, Int64Value.compareGe((Int64Value)val1, (Int64Value)val2));
else
return false;
}
bool emulate_Bge_Un() {
var val2 = instructionEmulator.pop();
var val1 = instructionEmulator.pop();
if (val1.valueType == ValueType.Int32 && val2.valueType == ValueType.Int32)
return emulateBranch(2, Int32Value.compareGe_Un((Int32Value)val1, (Int32Value)val2));
else if (val1.valueType == ValueType.Int64 && val2.valueType == ValueType.Int64)
return emulateBranch(2, Int64Value.compareGe_Un((Int64Value)val1, (Int64Value)val2));
else
return false;
}
bool emulate_Bgt() {
var val2 = instructionEmulator.pop();
var val1 = instructionEmulator.pop();
if (val1.valueType == ValueType.Int32 && val2.valueType == ValueType.Int32)
return emulateBranch(2, Int32Value.compareGt((Int32Value)val1, (Int32Value)val2));
else if (val1.valueType == ValueType.Int64 && val2.valueType == ValueType.Int64)
return emulateBranch(2, Int64Value.compareGt((Int64Value)val1, (Int64Value)val2));
else
return false;
}
bool emulate_Bgt_Un() {
var val2 = instructionEmulator.pop();
var val1 = instructionEmulator.pop();
if (val1.valueType == ValueType.Int32 && val2.valueType == ValueType.Int32)
return emulateBranch(2, Int32Value.compareGt_Un((Int32Value)val1, (Int32Value)val2));
else if (val1.valueType == ValueType.Int64 && val2.valueType == ValueType.Int64)
return emulateBranch(2, Int64Value.compareGt_Un((Int64Value)val1, (Int64Value)val2));
else
return false;
}
bool emulate_Ble() {
var val2 = instructionEmulator.pop();
var val1 = instructionEmulator.pop();
if (val1.valueType == ValueType.Int32 && val2.valueType == ValueType.Int32)
return emulateBranch(2, Int32Value.compareLe((Int32Value)val1, (Int32Value)val2));
else if (val1.valueType == ValueType.Int64 && val2.valueType == ValueType.Int64)
return emulateBranch(2, Int64Value.compareLe((Int64Value)val1, (Int64Value)val2));
else
return false;
}
bool emulate_Ble_Un() {
var val2 = instructionEmulator.pop();
var val1 = instructionEmulator.pop();
if (val1.valueType == ValueType.Int32 && val2.valueType == ValueType.Int32)
return emulateBranch(2, Int32Value.compareLe_Un((Int32Value)val1, (Int32Value)val2));
else if (val1.valueType == ValueType.Int64 && val2.valueType == ValueType.Int64)
return emulateBranch(2, Int64Value.compareLe_Un((Int64Value)val1, (Int64Value)val2));
else
return false;
}
bool emulate_Blt() {
var val2 = instructionEmulator.pop();
var val1 = instructionEmulator.pop();
if (val1.valueType == ValueType.Int32 && val2.valueType == ValueType.Int32)
return emulateBranch(2, Int32Value.compareLt((Int32Value)val1, (Int32Value)val2));
else if (val1.valueType == ValueType.Int64 && val2.valueType == ValueType.Int64)
return emulateBranch(2, Int64Value.compareLt((Int64Value)val1, (Int64Value)val2));
else
return false;
}
bool emulate_Blt_Un() {
var val2 = instructionEmulator.pop();
var val1 = instructionEmulator.pop();
if (val1.valueType == ValueType.Int32 && val2.valueType == ValueType.Int32)
return emulateBranch(2, Int32Value.compareLt_Un((Int32Value)val1, (Int32Value)val2));
else if (val1.valueType == ValueType.Int64 && val2.valueType == ValueType.Int64)
return emulateBranch(2, Int64Value.compareLt_Un((Int64Value)val1, (Int64Value)val2));
else
return false;
}
bool emulate_Brfalse() {
var val1 = instructionEmulator.pop();
if (val1.valueType == ValueType.Int32)
return emulateBranch(1, Int32Value.compareFalse((Int32Value)val1));
else if (val1.valueType == ValueType.Int64)
return emulateBranch(1, Int64Value.compareFalse((Int64Value)val1));
else if (val1.valueType == ValueType.Null)
return emulateBranch(1, true);
else
return false;
}
bool emulate_Brtrue() {
var val1 = instructionEmulator.pop();
if (val1.valueType == ValueType.Int32)
return emulateBranch(1, Int32Value.compareTrue((Int32Value)val1));
else if (val1.valueType == ValueType.Int64)
return emulateBranch(1, Int64Value.compareTrue((Int64Value)val1));
else if (val1.valueType == ValueType.Null)
return emulateBranch(1, false);
else
return false;
}
}
}