/*
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;
using System.Collections.Generic;
using dot10.DotNet;
using dot10.DotNet.Emit;
using de4dot.blocks;
namespace de4dot.code.deobfuscators.DeepSea {
// DS 4.x can move fields from a class to a struct. This class restores the fields.
class FieldsRestorer {
ModuleDefMD module;
TypeDefDict> structToOwners = new TypeDefDict>();
FieldDefAndDeclaringTypeDict structFieldsToFix = new FieldDefAndDeclaringTypeDict();
TypeDefDict> typeToFieldsDict = new TypeDefDict>();
public List FieldStructs {
get {
var list = new List(structToOwners.Count);
foreach (var structType in structToOwners.getKeys()) {
if (!hasNoMethods(structType))
continue;
list.Add(structType);
}
return list;
}
}
static bool hasNoMethods(TypeDef type) {
if (type.Methods.Count == 0)
return true;
if (type.BaseType == null)
return false;
if (type.BaseType.FullName != "System.Object")
return false;
if (type.Methods.Count != 1)
return false;
var ctor = type.Methods[0];
if (ctor.Name != ".ctor" || ctor.MethodSig.GetParamCount() != 0)
return false;
return true;
}
public FieldsRestorer(ModuleDefMD module) {
this.module = module;
}
public void initialize() {
foreach (var kv in getMovedTypes()) {
var structType = kv.Key;
structToOwners.add(structType, kv.Value);
foreach (var ownerType in kv.Value) {
foreach (var ownerField in ownerType.Fields) {
if (DotNetUtils.getType(module, ownerField.FieldSig.GetFieldType()) != structType)
continue;
structFieldsToFix.add(ownerField, true);
break;
}
var fieldsDict = new FieldDefAndDeclaringTypeDict();
typeToFieldsDict.add(ownerType, fieldsDict);
foreach (var structField in structType.Fields) {
var newField = module.UpdateRowId(new FieldDefUser(structField.Name, structField.FieldSig.Clone(), structField.Attributes));
ownerType.Fields.Add(newField);
fieldsDict.add(structField, newField);
}
}
}
}
Dictionary> getMovedTypes() {
var candidates = new Dictionary>();
var typeToStruct = new Dictionary();
foreach (var type in module.GetTypes()) {
foreach (var field in getPossibleFields(type)) {
var fieldType = DotNetUtils.getType(module, field.FieldSig.GetFieldType());
if (fieldType == null)
continue;
if (!checkBaseType(fieldType))
continue;
if ((fieldType.Attributes & ~TypeAttributes.Sealed) != TypeAttributes.NestedAssembly)
continue;
if (fieldType.NestedTypes.Count > 0)
continue;
if (fieldType.GenericParameters.Count > 0)
continue;
if (fieldType.Fields.Count == 0)
continue;
if (fieldType.HasEvents || fieldType.HasProperties || fieldType.HasInterfaces)
continue;
if (checkMethods(fieldType))
continue;
if (!checkFields(fieldType))
continue;
List list;
if (!candidates.TryGetValue(fieldType, out list))
candidates[fieldType] = list = new List();
list.Add(type);
typeToStruct[type] = fieldType;
break;
}
}
foreach (var type in module.GetTypes()) {
TypeDef structType;
typeToStruct.TryGetValue(type, out structType);
foreach (var field in type.Fields) {
if (field.IsStatic || field.FieldSig.GetFieldType().TryGetTypeDef() != structType)
removeType(candidates, field.FieldSig.GetFieldType());
}
foreach (var method in type.Methods) {
removeType(candidates, method.MethodSig.GetRetType());
foreach (var parameter in method.MethodSig.GetParams())
removeType(candidates, parameter);
if (method.Body != null) {
foreach (var local in method.Body.Variables)
removeType(candidates, local.Type);
}
}
}
return candidates;
}
IEnumerable getPossibleFields(TypeDef type) {
var typeToFields = new TypeDefDict>();
foreach (var field in type.Fields) {
if (field.Attributes != FieldAttributes.Private)
continue;
var fieldType = DotNetUtils.getType(module, field.FieldSig.GetFieldType());
if (fieldType == null)
continue;
if (!checkBaseType(fieldType))
continue;
var list = typeToFields.find(fieldType);
if (list == null)
typeToFields.add(fieldType, list = new List());
list.Add(field);
}
foreach (var list in typeToFields.getValues()) {
if (list.Count == 1)
yield return list[0];
}
}
static bool checkBaseType(TypeDef type) {
if (type == null || type.BaseType == null)
return false;
var fn = type.BaseType.FullName;
return fn == "System.ValueType" || fn == "System.Object";
}
void removeType(Dictionary> candidates, TypeSig type) {
var typeDef = DotNetUtils.getType(module, type);
if (typeDef == null)
return;
candidates.Remove(typeDef);
}
static bool checkMethods(TypeDef type) {
foreach (var method in type.Methods) {
if (method.Name == ".cctor")
continue;
if (type.BaseType != null && type.BaseType.FullName == "System.Object" && method.Name == ".ctor" && method.MethodSig.GetParamCount() == 0)
continue;
if (!method.IsStatic)
return true;
if (method.GenericParameters.Count > 0)
return true;
if (method.Body == null)
return true;
if (method.ImplMap != null)
return true;
}
return false;
}
static bool checkFields(TypeDef type) {
if (type.Fields.Count == 0)
return false;
foreach (var field in type.Fields) {
if (field.IsStatic)
return false;
if (!field.IsAssembly)
return false;
}
return true;
}
public void deobfuscate(Blocks blocks) {
deobfuscateNormal(blocks);
fixFieldCtorCalls(blocks);
}
void deobfuscateNormal(Blocks blocks) {
var instrsToRemove = new List();
foreach (var block in blocks.MethodBlocks.getAllBlocks()) {
instrsToRemove.Clear();
var instrs = block.Instructions;
for (int i = instrs.Count - 1; i >= 0; i--) {
var instr = instrs[i];
if (instr.OpCode.Code != Code.Ldflda && instr.OpCode.Code != Code.Ldfld)
continue;
var structField = instr.Operand as IField;
if (structField == null || !structFieldsToFix.find(structField))
continue;
var ldStFld = instrs[findLdStFieldIndex(instrs, i + 1)];
ldStFld.Operand = getNewField(structField, ldStFld.Operand as IField);
instrsToRemove.Add(i);
}
if (instrsToRemove.Count > 0)
block.remove(instrsToRemove);
}
}
void fixFieldCtorCalls(Blocks blocks) {
if (blocks.Method.Name != ".ctor")
return;
var instrsToRemove = new List();
foreach (var block in blocks.MethodBlocks.getAllBlocks()) {
var instrs = block.Instructions;
for (int i = 0; i < instrs.Count; i++) {
var stfld = instrs[i];
if (stfld.OpCode.Code != Code.Stfld)
continue;
var field = stfld.Operand as IField;
if (field == null)
continue;
if (!structFieldsToFix.find(field))
continue;
var instrs2 = toInstructionList(instrs);
var instrPushes = DotNetUtils.getArgPushes(instrs2, i);
if (instrPushes == null || instrPushes.Count != 2)
continue;
block.remove(i, 1);
block.remove(instrs2.IndexOf(instrPushes[1]), 1);
block.remove(instrs2.IndexOf(instrPushes[0]), 1);
i -= 3;
}
}
}
static IList toInstructionList(IEnumerable instrs) {
var newInstrs = new List();
foreach (var instr in instrs)
newInstrs.Add(instr.Instruction);
return newInstrs;
}
FieldDef getNewField(IField structField, IField oldFieldRef) {
var fieldsDict = typeToFieldsDict.find(structField.DeclaringType);
if (fieldsDict == null)
throw new ApplicationException("Could not find structField declaringType");
var newField = fieldsDict.find(oldFieldRef);
if (newField == null)
throw new ApplicationException("Could not find new field");
return newField;
}
static int findLdStFieldIndex(IList instrs, int index) {
int stack = 0;
for (int i = index; i < instrs.Count; i++) {
var instr = instrs[i];
if (stack == 0 && (instr.OpCode.Code == Code.Ldfld || instr.OpCode.Code == Code.Ldflda))
return i;
if (stack == 1 && instr.OpCode.Code == Code.Stfld)
return i;
int pushes, pops;
instr.Instruction.CalculateStackUsage(false, out pushes, out pops);
stack -= pops;
if (stack < 0)
break;
stack += pushes;
}
throw new ApplicationException("Could not find ldfld/stfld");
}
public void cleanUp() {
foreach (var field in structFieldsToFix.getKeys())
field.DeclaringType.Fields.Remove(field);
}
}
}