/*
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 Mono.Cecil;
using Mono.Cecil.Cil;
using Mono.Cecil.Metadata;
using de4dot.blocks;
using de4dot.blocks.cflow;
namespace de4dot.code.deobfuscators.DeepSea {
class ArrayBlockDeobfuscator : BlockDeobfuscator {
ModuleDefinition module;
FieldDefinitionAndDeclaringTypeDict fieldToInfo = new FieldDefinitionAndDeclaringTypeDict();
Dictionary localToInfo = new Dictionary();
DsConstantsReader constantsReader;
class FieldInfo {
public readonly FieldDefinition field;
public readonly FieldDefinition arrayInitField;
public readonly byte[] array;
public FieldInfo(FieldDefinition field, FieldDefinition arrayInitField) {
this.field = field;
this.arrayInitField = arrayInitField;
this.array = (byte[])arrayInitField.InitialValue.Clone();
}
}
public bool Detected {
get { return fieldToInfo.Count != 0; }
}
public ArrayBlockDeobfuscator(ModuleDefinition module) {
this.module = module;
}
public void init() {
initializeArrays(DotNetUtils.getModuleTypeCctor(module));
}
void initializeArrays(MethodDefinition method) {
if (method == null || method.Body == null)
return;
var instructions = method.Body.Instructions;
for (int i = 0; i < instructions.Count; i++) {
var ldci4 = instructions[i];
if (!DotNetUtils.isLdcI4(ldci4))
continue;
i++;
var instrs = DotNetUtils.getInstructions(instructions, i, OpCodes.Newarr, OpCodes.Dup, OpCodes.Ldtoken, OpCodes.Call, OpCodes.Stsfld);
if (instrs == null)
continue;
var arrayType = instrs[0].Operand as TypeReference;
if (arrayType == null || arrayType.EType != ElementType.U1)
continue;
var arrayInitField = instrs[2].Operand as FieldDefinition;
if (arrayInitField == null || arrayInitField.InitialValue == null || arrayInitField.InitialValue.Length == 0)
continue;
var calledMethod = instrs[3].Operand as MethodReference;
if (calledMethod == null || calledMethod.FullName != "System.Void System.Runtime.CompilerServices.RuntimeHelpers::InitializeArray(System.Array,System.RuntimeFieldHandle)")
continue;
var targetField = instrs[4].Operand as FieldDefinition;
if (targetField == null)
continue;
fieldToInfo.add(targetField, new FieldInfo(targetField, arrayInitField));
}
}
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 = fieldToInfo.find((FieldReference)ldsfld.Operand);
if (info == null)
continue;
var local = DotNetUtils.getLocalVar(blocks.Locals, stloc.Instruction);
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;
}
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 = DotNetUtils.getLocalVar(blocks.Locals, ldloc.Instruction);
if (local == null)
return false;
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 (ldelem.OpCode.Code != Code.Ldelem_U1)
return false;
block.remove(i, 3 - 1);
instrs[i] = new Instr(DotNetUtils.createLdci4(info.array[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 = fieldToInfo.find(ldsfld.Operand as FieldReference);
if (info == null)
return false;
var ldci4 = instrs[i + 1];
if (!ldci4.isLdcI4())
return false;
var ldelem = instrs[i + 2];
if (ldelem.OpCode.Code != Code.Ldelem_U1)
return false;
block.remove(i, 3 - 1);
instrs[i] = new Instr(DotNetUtils.createLdci4(info.array[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 = fieldToInfo.find(ldsfld.Operand as FieldReference);
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 (stelem.OpCode.Code != Code.Stelem_I1)
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);
}
public IEnumerable cleanUp() {
var removedFields = new List();
var moduleCctor = DotNetUtils.getModuleTypeCctor(module);
if (moduleCctor == null)
return removedFields;
var moduleCctorBlocks = new Blocks(moduleCctor);
var keep = findFieldsToKeep();
foreach (var fieldInfo in fieldToInfo.getValues()) {
if (keep.ContainsKey(fieldInfo))
continue;
if (removeInitCode(moduleCctorBlocks, fieldInfo)) {
removedFields.Add(fieldInfo.field);
removedFields.Add(fieldInfo.arrayInitField);
}
fieldInfo.arrayInitField.InitialValue = new byte[1];
fieldInfo.arrayInitField.FieldType = module.TypeSystem.Byte;
}
IList allInstructions;
IList allExceptionHandlers;
moduleCctorBlocks.getCode(out allInstructions, out allExceptionHandlers);
DotNetUtils.restoreBody(moduleCctorBlocks.Method, allInstructions, allExceptionHandlers);
return removedFields;
}
bool removeInitCode(Blocks blocks, FieldInfo info) {
bool removedSomething = false;
foreach (var block in blocks.MethodBlocks.getAllBlocks()) {
var instrs = block.Instructions;
for (int i = 0; i < instrs.Count - 5; i++) {
var ldci4 = instrs[i];
if (!ldci4.isLdcI4())
continue;
if (instrs[i + 1].OpCode.Code != Code.Newarr)
continue;
if (instrs[i + 2].OpCode.Code != Code.Dup)
continue;
var ldtoken = instrs[i + 3];
if (ldtoken.OpCode.Code != Code.Ldtoken)
continue;
if (ldtoken.Operand != info.arrayInitField)
continue;
var call = instrs[i + 4];
if (call.OpCode.Code != Code.Call)
continue;
var calledMethod = call.Operand as MethodReference;
if (calledMethod == null || calledMethod.FullName != "System.Void System.Runtime.CompilerServices.RuntimeHelpers::InitializeArray(System.Array,System.RuntimeFieldHandle)")
continue;
var stsfld = instrs[i + 5];
if (stsfld.OpCode.Code != Code.Stsfld)
continue;
if (stsfld.Operand != info.field)
continue;
block.remove(i, 6);
i--;
removedSomething = true;
}
}
return removedSomething;
}
Dictionary findFieldsToKeep() {
var keep = new Dictionary();
foreach (var type in module.GetTypes()) {
foreach (var method in type.Methods) {
if (type == DotNetUtils.getModuleType(module) && method.Name == ".cctor")
continue;
if (method.Body == null)
continue;
foreach (var instr in method.Body.Instructions) {
var field = instr.Operand as FieldReference;
if (field == null)
continue;
var fieldInfo = fieldToInfo.find(field);
if (fieldInfo == null)
continue;
keep[fieldInfo] = true;
}
}
}
return keep;
}
}
}