2012-01-08 03:27:07 +08:00
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/*
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Copyright (C) 2011 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.Collections.Generic;
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using System.IO;
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using Mono.Cecil;
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using de4dot.blocks;
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namespace de4dot.code.deobfuscators.Babel_NET {
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class StringDecrypter {
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ModuleDefinition module;
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Dictionary<int, string> offsetToString = new Dictionary<int, string>();
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TypeDefinition decrypterType;
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MethodDefinition decryptMethod;
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EmbeddedResource encryptedResource;
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public bool Detected {
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get { return decrypterType != null; }
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}
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public TypeDefinition Type {
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get { return decrypterType; }
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}
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public MethodDefinition DecryptMethod {
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get { return decryptMethod; }
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}
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public EmbeddedResource Resource {
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get { return encryptedResource; }
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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 void find() {
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foreach (var type in module.Types) {
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if (!isDecrypterType(type))
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continue;
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var method = DotNetUtils.getMethod(type, "System.String", "(System.Int32)");
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if (method == null)
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continue;
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decrypterType = type;
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decryptMethod = method;
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return;
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}
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}
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bool isDecrypterType(TypeDefinition type) {
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if (type.HasEvents)
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return false;
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if (type.NestedTypes.Count != 1)
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return false;
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if (type.Fields.Count != 0)
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return false;
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var nested = type.NestedTypes[0];
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if (nested.HasProperties || nested.HasEvents)
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return false;
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2012-01-09 12:50:32 +08:00
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if (nested.Fields.Count == 1) {
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// 4.2+ (maybe 4.0+)
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if (!MemberReferenceHelper.compareTypes(nested.Fields[0].FieldType, nested))
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return false;
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if (DotNetUtils.getMethod(nested, "System.Reflection.Emit.MethodBuilder", "(System.Reflection.Emit.TypeBuilder)") == null)
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return false;
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}
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else if (nested.Fields.Count == 2) {
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// 3.5 and maybe earlier
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var field1 = nested.Fields[0];
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var field2 = nested.Fields[1];
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if (field1.FieldType.FullName != "System.Collections.Hashtable" && field2.FieldType.FullName != "System.Collections.Hashtable")
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return false;
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if (!MemberReferenceHelper.compareTypes(field1.FieldType, nested) && !MemberReferenceHelper.compareTypes(field2.FieldType, nested))
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return false;
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}
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else
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2012-01-08 03:27:07 +08:00
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return false;
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2012-01-09 12:50:32 +08:00
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if (DotNetUtils.getMethod(nested, ".ctor") == null)
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2012-01-08 03:27:07 +08:00
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return false;
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if (DotNetUtils.getMethod(nested, "System.String", "(System.Int32)") == null)
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return false;
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return true;
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}
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public void initialize() {
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if (decrypterType == null)
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return;
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if (encryptedResource != null)
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return;
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encryptedResource = findResource();
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if (encryptedResource == null)
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return;
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var decrypted = new ResourceDecrypter(module).decrypt(encryptedResource.GetResourceData());
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var reader = new BinaryReader(new MemoryStream(decrypted));
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while (reader.BaseStream.Position < reader.BaseStream.Length)
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offsetToString[(int)reader.BaseStream.Position] = reader.ReadString();
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}
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EmbeddedResource findResource() {
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foreach (var method in decrypterType.Methods) {
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foreach (var s in DotNetUtils.getCodeStrings(method)) {
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var resource = DotNetUtils.getResource(module, s) as EmbeddedResource;
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if (resource != null)
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return resource;
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}
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}
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return null;
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}
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public string decrypt(int offset) {
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return offsetToString[offset];
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}
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}
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}
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