301 lines
8.0 KiB
C#
301 lines
8.0 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 System.IO;
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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.Goliath_NET {
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abstract class DecrypterBase {
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protected ModuleDefMD module;
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EmbeddedResource encryptedResource;
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TypeDef decrypterType;
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TypeDef delegateType;
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TypeDef delegateInitType;
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protected BinaryReader decryptedReader;
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MethodDefAndDeclaringTypeDict<Info> decrypterMethods = new MethodDefAndDeclaringTypeDict<Info>();
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protected class Info {
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public MethodDef method;
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public int offset;
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public bool referenced = false;
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public Info(MethodDef method, int offset) {
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this.method = method;
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this.offset = offset;
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}
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}
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public bool Detected {
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get { return encryptedResource != null; }
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}
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public Resource EncryptedResource {
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get { return encryptedResource; }
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}
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public TypeDef Type {
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get { return decrypterType; }
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}
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public TypeDef DelegateInitType {
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get { return delegateInitType ?? FindDelegateInitType(); }
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}
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public TypeDef DelegateType {
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get { return delegateType; }
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}
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public IEnumerable<TypeDef> DecrypterTypes {
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get {
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var types = new TypeDefDict<TypeDef>();
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foreach (var info in decrypterMethods.GetValues()) {
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if (info.referenced)
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types.Add(info.method.DeclaringType, info.method.DeclaringType);
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}
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return types.GetValues();
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}
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}
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public DecrypterBase(ModuleDefMD module) {
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this.module = module;
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}
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protected Info GetInfo(MethodDef method) {
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var info = decrypterMethods.Find(method);
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if (info == null)
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return null;
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info.referenced = true;
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return info;
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}
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public void Find() {
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foreach (var tmp in module.Resources) {
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var resource = tmp as EmbeddedResource;
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if (resource == null)
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continue;
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if (!resource.Name.String.EndsWith(".resources", StringComparison.Ordinal))
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continue;
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string ns, name;
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SplitTypeName(resource.Name.String.Substring(0, resource.Name.String.Length - 10), out ns, out name);
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var type = new TypeRefUser(module, ns, name, module).Resolve();
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if (type == null)
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continue;
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if (!CheckDecrypterType(type))
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continue;
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encryptedResource = resource;
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decrypterType = type;
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break;
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}
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}
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protected abstract bool CheckDecrypterType(TypeDef type);
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void SplitTypeName(string fullName, out string ns, out string name) {
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int index = fullName.LastIndexOf('.');
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if (index < 0) {
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ns = "";
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name = fullName;
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}
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else {
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ns = fullName.Substring(0, index);
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name = fullName.Substring(index + 1);
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}
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}
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public void Initialize() {
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if (encryptedResource == null)
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return;
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decryptedReader = new BinaryReader(new MemoryStream(Decrypt(encryptedResource.GetResourceData())));
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delegateType = null;
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foreach (var type in module.GetTypes()) {
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var cctor = type.FindStaticConstructor();
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if (cctor == null)
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continue;
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if (type.Fields.Count != 1)
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continue;
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var field = type.Fields[0];
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var tmpDelegateType = DotNetUtils.GetType(module, field.FieldType);
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if (tmpDelegateType == null)
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continue;
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if (!CheckDelegateType(tmpDelegateType))
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continue;
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if (delegateType != null && delegateType != tmpDelegateType)
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continue;
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if (!CheckCctor(cctor))
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continue;
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delegateType = tmpDelegateType;
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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 (!method.IsStatic || method.Body == null)
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continue;
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var sig = method.MethodSig;
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if (sig == null || sig.Params.Count != 0)
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continue;
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if (sig.RetType.GetElementType() == ElementType.Void)
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continue;
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var info = GetDecrypterInfo(method, field);
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if (info == null)
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continue;
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decrypterMethods.Add(info.method, info);
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}
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}
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}
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Info GetDecrypterInfo(MethodDef method, FieldDef delegateField) {
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try {
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int index = 0;
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var instrs = method.Body.Instructions;
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if (instrs[index].OpCode.Code != Code.Ldsfld)
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return null;
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var field = instrs[index++].Operand as FieldDef;
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if (field != delegateField)
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return null;
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if (!instrs[index].IsLdcI4())
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return null;
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int offset = instrs[index++].GetLdcI4Value();
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if (instrs[index].OpCode.Code != Code.Call && instrs[index].OpCode.Code != Code.Callvirt)
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return null;
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var calledMethod = instrs[index++].Operand as IMethod;
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if (calledMethod.Name != "Invoke")
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return null;
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if (instrs[index].OpCode.Code == Code.Unbox_Any)
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index++;
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if (instrs[index++].OpCode.Code != Code.Ret)
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return null;
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return new Info(method, offset);
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}
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catch (ArgumentOutOfRangeException) {
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return null;
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}
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}
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bool CheckCctor(MethodDef cctor) {
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var ldtokenType = GetLdtokenType(cctor);
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if (!new SigComparer().Equals(ldtokenType, cctor.DeclaringType))
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return false;
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MethodDef initMethod = null;
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foreach (var method in DotNetUtils.GetCalledMethods(module, cctor)) {
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if (DotNetUtils.IsMethod(method, "System.Void", "(System.Type)")) {
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initMethod = method;
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break;
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}
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}
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if (initMethod == null || initMethod.Body == null)
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return false;
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return true;
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}
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static ITypeDefOrRef GetLdtokenType(MethodDef method) {
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if (method == null || method.Body == null)
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return null;
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foreach (var instr in method.Body.Instructions) {
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if (instr.OpCode.Code != Code.Ldtoken)
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continue;
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return instr.Operand as ITypeDefOrRef;
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}
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return null;
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}
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bool CheckDelegateType(TypeDef type) {
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if (!DotNetUtils.DerivesFromDelegate(type))
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return false;
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var invoke = type.FindMethod("Invoke");
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if (invoke == null)
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return false;
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return CheckDelegateInvokeMethod(invoke);
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}
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protected abstract bool CheckDelegateInvokeMethod(MethodDef invokeMethod);
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byte[] Decrypt(byte[] encryptedData) {
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const int KEY_LEN = 0x100;
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if (encryptedData.Length < KEY_LEN)
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throw new ApplicationException("Invalid encrypted data length");
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var decryptedData = new byte[encryptedData.Length - KEY_LEN];
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var pkt = PublicKey.GetRawData(PublicKeyBase.ToPublicKeyToken(module.Assembly.PublicKey));
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if (pkt == null || pkt.Length == 0)
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pkt = new byte[8];
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for (int i = 0, j = 0, ki = 0; i < decryptedData.Length; i++) {
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ki = (ki + 1) % (KEY_LEN - 1);
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j = (j + encryptedData[ki] + pkt[i % 8]) % (KEY_LEN - 1);
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var tmp = encryptedData[j];
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encryptedData[j] = encryptedData[ki];
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encryptedData[ki] = tmp;
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decryptedData[i] = (byte)(encryptedData[KEY_LEN + i] ^ encryptedData[(encryptedData[j] + encryptedData[ki]) % (KEY_LEN - 1)]);
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}
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return decryptedData;
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}
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TypeDef FindDelegateInitType() {
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if (delegateType == null)
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return null;
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foreach (var type in module.Types) {
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if (type.HasProperties || type.HasEvents || type.HasFields)
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continue;
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foreach (var method in type.Methods) {
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if (!method.IsStatic || method.IsPrivate || method.Body == null)
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continue;
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var ldtokenType = GetLdtokenType(method);
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if (ldtokenType == null)
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continue;
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if (!new SigComparer().Equals(ldtokenType, delegateType))
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continue;
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delegateInitType = type;
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return delegateInitType;
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}
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}
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return null;
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}
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public IEnumerable<MethodDef> GetMethods() {
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var list = new List<MethodDef>(decrypterMethods.Count);
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foreach (var info in decrypterMethods.GetValues())
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list.Add(info.method);
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return list;
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}
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}
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}
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