309 lines
9.4 KiB
C#
309 lines
9.4 KiB
C#
/*
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Copyright (C) 2011-2015 de4dot@gmail.com
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This file is part of de4dot.
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de4dot is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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de4dot is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with de4dot. If not, see <http://www.gnu.org/licenses/>.
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*/
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using System;
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using System.Collections.Generic;
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using dnlib.DotNet;
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using dnlib.DotNet.Emit;
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using de4dot.blocks;
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namespace de4dot.code.deobfuscators.DeepSea {
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// DS 4.x can move fields from a class to a struct. This class restores the fields.
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class FieldsRestorer {
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ModuleDefMD module;
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TypeDefDict<List<TypeDef>> structToOwners = new TypeDefDict<List<TypeDef>>();
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FieldDefAndDeclaringTypeDict<bool> structFieldsToFix = new FieldDefAndDeclaringTypeDict<bool>();
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TypeDefDict<FieldDefAndDeclaringTypeDict<FieldDef>> typeToFieldsDict = new TypeDefDict<FieldDefAndDeclaringTypeDict<FieldDef>>();
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public List<TypeDef> FieldStructs {
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get {
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var list = new List<TypeDef>(structToOwners.Count);
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foreach (var structType in structToOwners.GetKeys()) {
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if (!HasNoMethods(structType))
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continue;
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list.Add(structType);
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}
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return list;
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}
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}
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static bool HasNoMethods(TypeDef type) {
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if (type.Methods.Count == 0)
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return true;
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if (type.BaseType == null)
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return false;
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if (type.BaseType.FullName != "System.Object")
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return false;
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if (type.Methods.Count != 1)
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return false;
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var ctor = type.Methods[0];
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if (ctor.Name != ".ctor" || ctor.MethodSig.GetParamCount() != 0)
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return false;
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return true;
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}
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public FieldsRestorer(ModuleDefMD module) {
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this.module = module;
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}
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public void Initialize() {
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foreach (var kv in GetMovedTypes()) {
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var structType = kv.Key;
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structToOwners.Add(structType, kv.Value);
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foreach (var ownerType in kv.Value) {
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foreach (var ownerField in ownerType.Fields) {
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if (DotNetUtils.GetType(module, ownerField.FieldSig.GetFieldType()) != structType)
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continue;
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structFieldsToFix.Add(ownerField, true);
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break;
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}
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var fieldsDict = new FieldDefAndDeclaringTypeDict<FieldDef>();
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typeToFieldsDict.Add(ownerType, fieldsDict);
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foreach (var structField in structType.Fields) {
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var newField = module.UpdateRowId(new FieldDefUser(structField.Name, structField.FieldSig.Clone(), structField.Attributes));
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ownerType.Fields.Add(newField);
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fieldsDict.Add(structField, newField);
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}
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}
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}
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}
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Dictionary<TypeDef, List<TypeDef>> GetMovedTypes() {
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var candidates = new Dictionary<TypeDef, List<TypeDef>>();
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var typeToStruct = new Dictionary<TypeDef, TypeDef>();
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foreach (var type in module.GetTypes()) {
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foreach (var field in GetPossibleFields(type)) {
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var fieldType = DotNetUtils.GetType(module, field.FieldSig.GetFieldType());
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if (fieldType == null)
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continue;
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if (!CheckBaseType(fieldType))
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continue;
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if ((fieldType.Attributes & ~TypeAttributes.Sealed) != TypeAttributes.NestedAssembly)
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continue;
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if (fieldType.NestedTypes.Count > 0)
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continue;
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if (fieldType.GenericParameters.Count > 0)
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continue;
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if (fieldType.Fields.Count == 0)
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continue;
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if (fieldType.HasEvents || fieldType.HasProperties || fieldType.HasInterfaces)
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continue;
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if (CheckMethods(fieldType))
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continue;
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if (!CheckFields(fieldType))
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continue;
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List<TypeDef> list;
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if (!candidates.TryGetValue(fieldType, out list))
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candidates[fieldType] = list = new List<TypeDef>();
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list.Add(type);
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typeToStruct[type] = fieldType;
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break;
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}
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}
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foreach (var type in module.GetTypes()) {
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TypeDef structType;
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typeToStruct.TryGetValue(type, out structType);
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foreach (var field in type.Fields) {
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if (field.IsStatic || field.FieldSig.GetFieldType().TryGetTypeDef() != structType)
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RemoveType(candidates, field.FieldSig.GetFieldType());
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}
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foreach (var method in type.Methods) {
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RemoveType(candidates, method.MethodSig.GetRetType());
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foreach (var parameter in method.MethodSig.GetParams())
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RemoveType(candidates, parameter);
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if (method.Body != null) {
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foreach (var local in method.Body.Variables)
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RemoveType(candidates, local.Type);
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}
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}
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}
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return candidates;
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}
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IEnumerable<FieldDef> GetPossibleFields(TypeDef type) {
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var typeToFields = new TypeDefDict<List<FieldDef>>();
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foreach (var field in type.Fields) {
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if (field.Attributes != FieldAttributes.Private)
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continue;
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var fieldType = DotNetUtils.GetType(module, field.FieldSig.GetFieldType());
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if (fieldType == null)
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continue;
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if (!CheckBaseType(fieldType))
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continue;
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var list = typeToFields.Find(fieldType);
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if (list == null)
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typeToFields.Add(fieldType, list = new List<FieldDef>());
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list.Add(field);
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}
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foreach (var list in typeToFields.GetValues()) {
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if (list.Count == 1)
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yield return list[0];
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}
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}
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static bool CheckBaseType(TypeDef type) {
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if (type == null || type.BaseType == null)
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return false;
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var fn = type.BaseType.FullName;
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return fn == "System.ValueType" || fn == "System.Object";
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}
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void RemoveType(Dictionary<TypeDef, List<TypeDef>> candidates, TypeSig type) {
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var typeDef = DotNetUtils.GetType(module, type);
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if (typeDef == null)
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return;
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candidates.Remove(typeDef);
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}
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static bool CheckMethods(TypeDef type) {
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foreach (var method in type.Methods) {
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if (method.Name == ".cctor")
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continue;
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if (type.BaseType != null && type.BaseType.FullName == "System.Object" && method.Name == ".ctor" && method.MethodSig.GetParamCount() == 0)
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continue;
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if (!method.IsStatic)
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return true;
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if (method.GenericParameters.Count > 0)
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return true;
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if (method.Body == null)
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return true;
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if (method.ImplMap != null)
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return true;
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}
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return false;
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}
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static bool CheckFields(TypeDef type) {
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if (type.Fields.Count == 0)
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return false;
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foreach (var field in type.Fields) {
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if (field.IsStatic)
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return false;
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if (!field.IsAssembly)
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return false;
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}
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return true;
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}
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public void Deobfuscate(Blocks blocks) {
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DeobfuscateNormal(blocks);
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FixFieldCtorCalls(blocks);
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}
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void DeobfuscateNormal(Blocks blocks) {
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var instrsToRemove = new List<int>();
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foreach (var block in blocks.MethodBlocks.GetAllBlocks()) {
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instrsToRemove.Clear();
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var instrs = block.Instructions;
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for (int i = instrs.Count - 1; i >= 0; i--) {
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var instr = instrs[i];
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if (instr.OpCode.Code != Code.Ldflda && instr.OpCode.Code != Code.Ldfld)
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continue;
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var structField = instr.Operand as IField;
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if (structField == null || !structFieldsToFix.Find(structField))
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continue;
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var ldStFld = instrs[FindLdStFieldIndex(instrs, i + 1)];
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ldStFld.Operand = GetNewField(structField, ldStFld.Operand as IField);
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instrsToRemove.Add(i);
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}
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if (instrsToRemove.Count > 0)
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block.Remove(instrsToRemove);
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}
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}
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void FixFieldCtorCalls(Blocks blocks) {
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if (blocks.Method.Name != ".ctor")
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return;
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//var instrsToRemove = new List<int>();
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foreach (var block in blocks.MethodBlocks.GetAllBlocks()) {
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var instrs = block.Instructions;
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for (int i = 0; i < instrs.Count; i++) {
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var stfld = instrs[i];
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if (stfld.OpCode.Code != Code.Stfld)
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continue;
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var field = stfld.Operand as IField;
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if (field == null)
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continue;
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if (!structFieldsToFix.Find(field))
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continue;
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var instrs2 = ToInstructionList(instrs);
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var instrPushes = DotNetUtils.GetArgPushes(instrs2, i);
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if (instrPushes == null || instrPushes.Count != 2)
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continue;
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block.Remove(i, 1);
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block.Remove(instrs2.IndexOf(instrPushes[1]), 1);
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block.Remove(instrs2.IndexOf(instrPushes[0]), 1);
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i -= 3;
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}
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}
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}
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static IList<Instruction> ToInstructionList(IEnumerable<Instr> instrs) {
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var newInstrs = new List<Instruction>();
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foreach (var instr in instrs)
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newInstrs.Add(instr.Instruction);
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return newInstrs;
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}
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FieldDef GetNewField(IField structField, IField oldFieldRef) {
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var fieldsDict = typeToFieldsDict.Find(structField.DeclaringType);
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if (fieldsDict == null)
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throw new ApplicationException("Could not find structField declaringType");
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var newField = fieldsDict.Find(oldFieldRef);
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if (newField == null)
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throw new ApplicationException("Could not find new field");
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return newField;
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}
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static int FindLdStFieldIndex(IList<Instr> instrs, int index) {
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int stack = 0;
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for (int i = index; i < instrs.Count; i++) {
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var instr = instrs[i];
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if (stack == 0 && (instr.OpCode.Code == Code.Ldfld || instr.OpCode.Code == Code.Ldflda))
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return i;
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if (stack == 1 && instr.OpCode.Code == Code.Stfld)
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return i;
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int pushes, pops;
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instr.Instruction.CalculateStackUsage(false, out pushes, out pops);
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stack -= pops;
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if (stack < 0)
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break;
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stack += pushes;
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}
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throw new ApplicationException("Could not find ldfld/stfld");
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}
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public void CleanUp() {
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foreach (var field in structFieldsToFix.GetKeys())
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field.DeclaringType.Fields.Remove(field);
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}
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}
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}
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