Add string decrypter
This commit is contained in:
de4dot
parent
029c049bf6
commit
d6ff8b515d
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@ -81,6 +81,7 @@
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<Compile Include="deobfuscators\CliSecure\StringDecrypter.cs" />
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<Compile Include="deobfuscators\CodeVeil\Deobfuscator.cs" />
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<Compile Include="deobfuscators\CodeVeil\MethodsDecrypter.cs" />
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<Compile Include="deobfuscators\CodeVeil\StringDecrypter.cs" />
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<Compile Include="deobfuscators\CryptoObfuscator\AntiDebugger.cs" />
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<Compile Include="deobfuscators\CryptoObfuscator\AssemblyResolver.cs" />
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<Compile Include="deobfuscators\CryptoObfuscator\Deobfuscator.cs" />
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@ -57,6 +57,7 @@ namespace de4dot.code.deobfuscators.CodeVeil {
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bool foundKillType = false;
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MethodsDecrypter methodsDecrypter;
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StringDecrypter stringDecrypter;
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internal class Options : OptionsBase {
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}
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@ -82,7 +83,8 @@ namespace de4dot.code.deobfuscators.CodeVeil {
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int val = 0;
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int sum = toInt32(foundKillType) +
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toInt32(methodsDecrypter.Detected);
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toInt32(methodsDecrypter.Detected) +
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toInt32(stringDecrypter.Detected);
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if (sum > 0)
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val += 100 + 10 * (sum - 1);
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@ -93,12 +95,15 @@ namespace de4dot.code.deobfuscators.CodeVeil {
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findKillType();
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methodsDecrypter = new MethodsDecrypter(module);
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methodsDecrypter.find();
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stringDecrypter = new StringDecrypter(module);
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stringDecrypter.find();
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}
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void findKillType() {
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foreach (var type in module.Types) {
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if (type.FullName == "____KILL") {
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addTypeToBeRemoved(type, "KILL type");
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foundKillType = true;
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break;
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}
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}
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@ -120,12 +125,22 @@ namespace de4dot.code.deobfuscators.CodeVeil {
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var newOne = new Deobfuscator(options);
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newOne.setModule(module);
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newOne.methodsDecrypter = new MethodsDecrypter(module, methodsDecrypter);
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newOne.stringDecrypter = new StringDecrypter(module, stringDecrypter);
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return newOne;
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}
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public override void deobfuscateBegin() {
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base.deobfuscateBegin();
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if (Operations.DecryptStrings != OpDecryptString.None) {
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stringDecrypter.initialize();
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staticStringInliner.add(stringDecrypter.DecryptMethod, (method, args) => {
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return stringDecrypter.decrypt((int)args[0]);
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});
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DeobfuscatedFile.stringDecryptersAdded();
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}
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//TODO:
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}
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232
de4dot.code/deobfuscators/CodeVeil/StringDecrypter.cs
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232
de4dot.code/deobfuscators/CodeVeil/StringDecrypter.cs
Normal file
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@ -0,0 +1,232 @@
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/*
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Copyright (C) 2011-2012 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.IO;
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using Mono.Cecil;
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using Mono.Cecil.Cil;
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using de4dot.blocks;
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namespace de4dot.code.deobfuscators.CodeVeil {
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class StringDecrypter {
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ModuleDefinition module;
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TypeDefinition decrypterType;
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FieldDefinition stringDataField;
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MethodDefinition initMethod;
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MethodDefinition decrypterMethod;
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string[] decryptedStrings;
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public bool Detected {
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get { return decrypterType != null; }
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}
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public MethodDefinition DecryptMethod {
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get { return decrypterMethod; }
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}
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public StringDecrypter(ModuleDefinition module) {
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this.module = module;
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}
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public StringDecrypter(ModuleDefinition module, StringDecrypter oldOne) {
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this.module = module;
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this.decrypterType = lookup(oldOne.decrypterType, "Could not find string decrypter type");
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this.stringDataField = lookup(oldOne.stringDataField, "Could not find string data field");
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this.initMethod = lookup(oldOne.initMethod, "Could not find string decrypter init method");
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this.decrypterMethod = lookup(oldOne.decrypterMethod, "Could not find string decrypter method");
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}
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T lookup<T>(T def, string errorMessage) where T : MemberReference {
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return DeobUtils.lookup(module, def, errorMessage);
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}
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public void find() {
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var cctor = DotNetUtils.getModuleTypeCctor(module);
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if (cctor == null)
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return;
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var instrs = cctor.Body.Instructions;
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for (int i = 0; i < instrs.Count; i++) {
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var call = instrs[i];
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if (call.OpCode.Code != Code.Call)
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continue;
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var initMethodTmp = call.Operand as MethodDefinition;
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if (initMethodTmp == null || initMethodTmp.Body == null || !initMethodTmp.IsStatic)
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continue;
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if (!DotNetUtils.isMethod(initMethodTmp, "System.Void", "()"))
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continue;
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if (!checkType(initMethodTmp.DeclaringType))
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continue;
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decrypterType = initMethodTmp.DeclaringType;
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initMethod = initMethodTmp;
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break;
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}
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}
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bool checkType(TypeDefinition type) {
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if (!type.HasNestedTypes)
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return false;
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var stringDataFieldTmp = checkFields(type);
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if (stringDataFieldTmp == null)
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return false;
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var fieldType = DotNetUtils.getType(module, stringDataFieldTmp.FieldType);
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if (fieldType == null || type.NestedTypes.IndexOf(fieldType) < 0)
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return false;
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var decrypterMethodTmp = getDecrypterMethod(type);
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if (decrypterMethodTmp == null)
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return false;
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stringDataField = stringDataFieldTmp;
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decrypterMethod = decrypterMethodTmp;
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return true;
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}
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static MethodDefinition getDecrypterMethod(TypeDefinition type) {
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MethodDefinition foundMethod = null;
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foreach (var method in type.Methods) {
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if (method.Body == null || !method.IsStatic)
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continue;
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if (!DotNetUtils.isMethod(method, "System.String", "(System.Int32)"))
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continue;
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if (foundMethod != null)
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return null;
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foundMethod = method;
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}
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return foundMethod;
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}
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static string[] requiredFields = new string[] {
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"System.Byte[]",
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"System.Int32",
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"System.Int32[]",
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"System.String[]",
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"System.UInt32[]",
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};
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FieldDefinition checkFields(TypeDefinition type) {
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if (!new FieldTypes(type).all(requiredFields))
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return null;
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FieldDefinition stringData = null;
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foreach (var field in type.Fields) {
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if (field.RVA != 0) {
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if (stringData != null)
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return null;
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stringData = field;
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continue;
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}
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}
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if (stringData == null)
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return null;
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var data = stringData.InitialValue;
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if (data == null || data.Length == 0 || data.Length % 4 != 0)
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return null;
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return stringData;
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}
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public void initialize() {
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if (stringDataField == null)
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return;
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var key = getKey(initMethod);
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if (key == null)
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throw new ApplicationException("Could not find string decrypter key");
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decryptStrings(key);
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}
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static uint[] getKey(MethodDefinition method) {
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var instrs = method.Body.Instructions;
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for (int i = 0; i < instrs.Count - 1; i++) {
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var ldci4 = instrs[i];
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if (!DotNetUtils.isLdcI4(ldci4))
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continue;
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if (DotNetUtils.getLdcI4Value(ldci4) != 4)
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continue;
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if (instrs[i + 1].OpCode.Code != Code.Newarr)
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continue;
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i++;
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var ary = ArrayFinder.getInitializedInt32Array(4, method, ref i);
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if (ary == null)
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continue;
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var key = new uint[4];
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for (int j = 0; j < key.Length; j++)
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key[j] = (uint)ary[j];
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return key;
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}
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return null;
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}
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void decryptStrings(uint[] key) {
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var data = stringDataField.InitialValue;
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var encryptedData = new uint[data.Length / 4];
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Buffer.BlockCopy(data, 0, encryptedData, 0, data.Length);
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decryptXxtea(encryptedData, encryptedData.Length, key);
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var decryptedData = new byte[data.Length];
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Buffer.BlockCopy(encryptedData, 0, decryptedData, 0, data.Length);
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var inflated = DeobUtils.inflate(decryptedData, 0, decryptedData.Length, true);
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var reader = new BinaryReader(new MemoryStream(inflated));
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int deflatedLength = DeobUtils.readVariableLengthInteger(reader);
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int numStrings = DeobUtils.readVariableLengthInteger(reader);
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decryptedStrings = new string[numStrings];
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var offsets = new int[numStrings];
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for (int i = 0; i < numStrings; i++)
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offsets[i] = DeobUtils.readVariableLengthInteger(reader);
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int startOffset = (int)reader.BaseStream.Position;
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for (int i = 0; i < numStrings; i++) {
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reader.BaseStream.Position = startOffset + offsets[i];
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decryptedStrings[i] = reader.ReadString();
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}
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}
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// Code converted from C implementation @ http://en.wikipedia.org/wiki/XXTEA (btea() func)
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static void decryptXxtea(uint[] v, int n, uint[] key) {
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const uint DELTA = 0x9E3779B9;
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uint rounds = (uint)(6 + 52 / n);
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uint sum = rounds * DELTA;
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uint y = v[0];
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uint z;
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//#define MX (((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4)) ^ ((sum ^ y) + (key[(p & 3) ^ e] ^ z)))
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do {
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int e = (int)((sum >> 2) & 3);
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int p;
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for (p = n - 1; p > 0; p--) {
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z = v[p - 1];
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y = v[p] -= (((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4)) ^ ((sum ^ y) + (key[(p & 3) ^ e] ^ z)));
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}
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z = v[n - 1];
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y = v[0] -= (((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4)) ^ ((sum ^ y) + (key[(p & 3) ^ e] ^ z)));
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} while ((sum -= DELTA) != 0);
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}
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public string decrypt(int index) {
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return decryptedStrings[index];
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}
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}
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}
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