207 lines
6.5 KiB
C#
207 lines
6.5 KiB
C#
/*
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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.Collections.Generic;
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using System.IO;
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using System.Security.Cryptography;
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using System.Text;
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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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using de4dot.code.resources;
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namespace de4dot.code.deobfuscators.CodeWall {
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class AssemblyDecrypter {
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ModuleDefinition module;
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ISimpleDeobfuscator simpleDeobfuscator;
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IDeobfuscator deob;
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List<AssemblyInfo> assemblyInfos = new List<AssemblyInfo>();
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string entryPointAssemblyKey;
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string resourcePassword;
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string resourceSalt;
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EmbeddedResource assemblyResource;
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public class AssemblyInfo {
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public readonly byte[] data;
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public readonly string extension;
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public readonly string assemblyFullName;
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public readonly string assemblySimpleName;
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public readonly bool isEntryPointAssembly;
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public AssemblyInfo(byte[] data, string extension, string assemblyFullName, string assemblySimpleName, bool isEntryPointAssembly) {
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this.data = data;
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this.extension = extension;
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this.assemblyFullName = assemblyFullName;
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this.assemblySimpleName = assemblySimpleName;
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this.isEntryPointAssembly = isEntryPointAssembly;
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}
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public override string ToString() {
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return assemblyFullName;
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}
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}
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public IEnumerable<AssemblyInfo> AssemblyInfos {
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get { return assemblyInfos; }
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}
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public AssemblyDecrypter(ModuleDefinition module, ISimpleDeobfuscator simpleDeobfuscator, IDeobfuscator deob) {
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this.module = module;
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this.simpleDeobfuscator = simpleDeobfuscator;
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this.deob = deob;
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}
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static readonly string[] requiredLocals = new string[] {
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"System.AppDomain",
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"System.DateTime",
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};
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public void find() {
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var method = module.EntryPoint;
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if (!checkEntryPoint(method))
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return;
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MethodDefinition decryptAssemblyMethod;
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var mainKey = getMainResourceKey(method, out decryptAssemblyMethod);
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if (mainKey == null)
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return;
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deobfuscateAll(decryptAssemblyMethod);
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var resource = getResource(decryptAssemblyMethod);
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if (resource == null)
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return;
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string password, salt;
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if (!getPassword(decryptAssemblyMethod, out password, out salt))
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return;
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entryPointAssemblyKey = mainKey;
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resourcePassword = password;
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resourceSalt = salt;
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assemblyResource = resource;
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decryptAllAssemblies();
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}
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bool checkEntryPoint(MethodDefinition method) {
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if (method == null)
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return false;
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if (!new LocalTypes(method).all(requiredLocals))
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return false;
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var handlers = DeobUtils.getAllResolveHandlers(method);
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if (handlers.Count != 1)
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return false;
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return true;
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}
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void deobfuscateAll(MethodDefinition method) {
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simpleDeobfuscator.deobfuscate(method);
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simpleDeobfuscator.decryptStrings(method, deob);
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}
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string getMainResourceKey(MethodDefinition method, out MethodDefinition decryptAssemblyMethod) {
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foreach (var calledMethod in DotNetUtils.getCalledMethods(module, method)) {
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if (!calledMethod.IsStatic || calledMethod.Body == null)
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continue;
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if (!DotNetUtils.isMethod(calledMethod, "System.Void", "(System.String[])"))
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continue;
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deobfuscateAll(calledMethod);
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string keyInfo = getMainResourceKeyInfo(calledMethod, out decryptAssemblyMethod);
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if (keyInfo == null)
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continue;
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return BitConverter.ToString(new MD5CryptoServiceProvider().ComputeHash(new ASCIIEncoding().GetBytes(keyInfo))).Replace("-", "");
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}
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decryptAssemblyMethod = null;
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return null;
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}
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string getMainResourceKeyInfo(MethodDefinition method, out MethodDefinition decryptAssemblyMethod) {
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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 ldstr = instrs[i];
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if (ldstr.OpCode.Code != Code.Ldstr)
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continue;
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var call = instrs[i + 1];
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if (call.OpCode.Code != Code.Call)
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continue;
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var calledMethod = call.Operand as MethodDefinition;
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if (calledMethod == null)
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continue;
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decryptAssemblyMethod = calledMethod;
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return (string)ldstr.Operand;
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}
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decryptAssemblyMethod = null;
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return null;
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}
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EmbeddedResource getResource(MethodDefinition method) {
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foreach (var s in DotNetUtils.getCodeStrings(method)) {
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var resource = DotNetUtils.getResource(module, s + ".resources") as EmbeddedResource;
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if (resource != null)
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return resource;
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}
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return null;
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}
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bool getPassword(MethodDefinition method, out string password, out string salt) {
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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 ldstr1 = instrs[i];
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if (ldstr1.OpCode.Code != Code.Ldstr)
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continue;
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var ldstr2 = instrs[i + 1];
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if (ldstr2.OpCode.Code != Code.Ldstr)
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continue;
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password = (string)ldstr1.Operand;
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salt = (string)ldstr2.Operand;
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if (password == null || salt == null)
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continue;
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return true;
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}
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password = null;
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salt = null;
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return false;
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}
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void decryptAllAssemblies() {
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if (assemblyResource == null)
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return;
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var resourceSet = ResourceReader.read(module, assemblyResource.GetResourceStream());
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foreach (var resourceElement in resourceSet.ResourceElements) {
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if (resourceElement.ResourceData.Code != ResourceTypeCode.ByteArray)
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throw new ApplicationException("Invalid resource");
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var resourceData = (BuiltInResourceData)resourceElement.ResourceData;
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var assemblyData = decrypt((byte[])resourceData.Data);
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var theModule = ModuleDefinition.ReadModule(new MemoryStream(assemblyData));
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bool isMain = resourceElement.Name == entryPointAssemblyKey;
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assemblyInfos.Add(new AssemblyInfo(assemblyData, DeobUtils.getExtension(theModule.Kind), theModule.Assembly.FullName, theModule.Assembly.Name.Name, isMain));
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}
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}
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byte[] decrypt(byte[] encrypted) {
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var keyGenerator = new PasswordDeriveBytes(resourcePassword, Encoding.ASCII.GetBytes(resourceSalt));
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return DeobUtils.inflate(DeobUtils.aesDecrypt(encrypted, keyGenerator.GetBytes(32), keyGenerator.GetBytes(16)), false);
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}
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}
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}
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