320 lines
8.8 KiB
C#
320 lines
8.8 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 System.Text;
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using dnlib.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.CodeWall {
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class StringDecrypter {
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ModuleDefMD module;
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MethodDefAndDeclaringTypeDict<StringEncrypterInfo> stringEncrypterInfos = new MethodDefAndDeclaringTypeDict<StringEncrypterInfo>();
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Version version;
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public enum Version {
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Unknown,
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V30, // 3.0 - 3.5
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V36, // 3.6 - 4.1
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}
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public class StringEncrypterInfo {
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MethodDef method;
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public TypeDef Type {
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get { return method.DeclaringType; }
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}
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public MethodDef Method {
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get { return method; }
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}
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public EmbeddedResource Resource { get; set; }
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public int Magic1 { get; set; }
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public int Magic2 { get; set; }
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public int Magic3 { get; set; }
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public IBinaryReader Reader { get; set; }
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public StringEncrypterInfo(MethodDef method) {
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this.method = method;
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}
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public string Decrypt(int magic1, int magic2, int magic3) {
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int dataLen = magic3 ^ Magic3;
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var key = GetKey(magic1 ^ Magic1, dataLen);
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Reader.Position = GetDataOffset(magic2);
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var data = Reader.ReadBytes(dataLen);
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for (int i = 0; i < dataLen; i++)
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data[i] ^= key[i];
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return Encoding.Unicode.GetString(data);
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}
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byte[] GetKey(int seed, int keyLen) {
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var random = new Random(seed);
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var key = new byte[keyLen];
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random.NextBytes(key);
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return key;
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}
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int GetDataOffset(int magic2) {
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var pkt = GetPublicKeyToken();
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if (pkt == null)
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return magic2 ^ Magic2;
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else
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return magic2 ^ BitConverter.ToInt32(pkt, 0) ^ BitConverter.ToInt32(pkt, 4);
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}
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byte[] GetPublicKeyToken() {
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var module = method.Module;
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if (module.Assembly == null || PublicKeyBase.IsNullOrEmpty2(module.Assembly.PublicKey))
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return null;
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return module.Assembly.PublicKeyToken.Data;
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}
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public override string ToString() {
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return string.Format("{0:X8} M1:{1:X8} M2:{2:X8} M3:{3:X8}",
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Method.MDToken.ToInt32(),
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Magic1, Magic2, Magic3);
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}
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}
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public bool Detected {
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get { return stringEncrypterInfos.Count != 0; }
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}
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public Version TheVersion {
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get { return version; }
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}
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public IEnumerable<StringEncrypterInfo> Infos {
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get {
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var list = new List<StringEncrypterInfo>();
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foreach (var info in stringEncrypterInfos.GetValues()) {
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if (info.Resource != null)
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list.Add(info);
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}
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return list;
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}
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}
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public StringDecrypter(ModuleDefMD 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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MethodDef decrypterMethod;
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var decrypterVersion = CheckType(type, out decrypterMethod);
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if (decrypterVersion == Version.Unknown)
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continue;
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version = decrypterVersion;
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stringEncrypterInfos.Add(decrypterMethod, new StringEncrypterInfo(decrypterMethod));
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}
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}
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Version CheckType(TypeDef type, out MethodDef decrypterMethod) {
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MethodDef method;
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if ((method = CheckTypeV30(type)) != null) {
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decrypterMethod = method;
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return Version.V30;
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}
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if ((method = CheckTypeV36(type)) != null) {
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decrypterMethod = method;
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return Version.V36;
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}
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decrypterMethod = null;
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return Version.Unknown;
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}
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static readonly string[] requiredTypes_v30 = new string[] {
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"System.Collections.Generic.Dictionary`2<System.Int32,System.String>",
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};
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static readonly string[] requiredLocals_v30 = new string[] {
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"System.Int32",
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"System.Byte[]",
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"System.Reflection.Assembly",
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"System.IO.Stream",
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"System.Random",
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"System.String",
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};
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MethodDef CheckTypeV30(TypeDef type) {
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MethodDef decrypterMethod = CheckMethodsV30(type);
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if (decrypterMethod == null)
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return null;
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if (!new FieldTypes(type).Exactly(requiredTypes_v30))
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return null;
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if (!new LocalTypes(decrypterMethod).Exactly(requiredLocals_v30))
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return null;
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return decrypterMethod;
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}
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static MethodDef CheckMethodsV30(TypeDef type) {
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if (type.Methods.Count < 1 || type.Methods.Count > 2)
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return null;
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MethodDef decrypterMethod = null;
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//MethodDef cctor = null;
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foreach (var method in type.Methods) {
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if (method.Name == ".cctor") {
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//cctor = method;
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continue;
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}
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if (decrypterMethod != null)
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return null;
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if (!DotNetUtils.IsMethod(method, "System.String", "(System.Int32,System.Int32,System.Int32)"))
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return null;
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decrypterMethod = method;
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}
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if (decrypterMethod == null || !decrypterMethod.IsStatic)
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return null;
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return decrypterMethod;
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}
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static readonly string[] requiredTypes_v36 = new string[] {
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"System.Object",
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"System.Collections.Generic.Dictionary`2<System.Int32,System.String>",
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};
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static readonly string[] requiredLocals_v36 = new string[] {
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"System.Int32",
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"System.Byte[]",
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"System.Reflection.Assembly",
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"System.IO.Stream",
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"System.Random",
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"System.String",
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"System.Object",
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};
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MethodDef CheckTypeV36(TypeDef type) {
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MethodDef decrypterMethod = CheckMethodsV36(type);
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if (decrypterMethod == null)
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return null;
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if (!new FieldTypes(type).Exactly(requiredTypes_v36))
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return null;
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if (!new LocalTypes(decrypterMethod).Exactly(requiredLocals_v36))
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return null;
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return decrypterMethod;
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}
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static MethodDef CheckMethodsV36(TypeDef type) {
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if (type.Methods.Count != 2)
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return null;
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MethodDef decrypterMethod = null;
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MethodDef cctor = null;
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foreach (var method in type.Methods) {
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if (method.Name == ".cctor") {
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cctor = method;
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continue;
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}
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if (decrypterMethod != null)
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return null;
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if (!DotNetUtils.IsMethod(method, "System.String", "(System.Int32,System.Int32,System.Int32)"))
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return null;
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decrypterMethod = method;
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}
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if (cctor == null)
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return null;
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if (decrypterMethod == null || !decrypterMethod.IsStatic)
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return null;
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return decrypterMethod;
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}
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public void Initialize(ISimpleDeobfuscator simpleDeobfuscator) {
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foreach (var info in stringEncrypterInfos.GetValues()) {
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simpleDeobfuscator.Deobfuscate(info.Method);
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info.Resource = FindResource(info.Method);
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if (info.Resource == null) {
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Logger.w("Could not find encrypted strings resource (Method {0:X8})", info.Method.MDToken.ToInt32());
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continue;
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}
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info.Magic1 = FindMagic1(info.Method);
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info.Magic2 = FindMagic2(info.Method);
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info.Magic3 = FindMagic3(info.Method);
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info.Reader = info.Resource.Data;
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info.Reader.Position = 0;
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}
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}
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EmbeddedResource FindResource(MethodDef method) {
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return DotNetUtils.GetResource(module, DotNetUtils.GetCodeStrings(method)) as EmbeddedResource;
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}
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static int FindMagic1(MethodDef method) {
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var instrs = method.Body.Instructions;
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for (int i = 0; i < instrs.Count - 2; i++) {
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var ldarg = instrs[i];
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if (!ldarg.IsLdarg() || ldarg.GetParameterIndex() != 0)
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continue;
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var ldci4 = instrs[i + 1];
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if (!ldci4.IsLdcI4())
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continue;
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if (instrs[i + 2].OpCode.Code != Code.Xor)
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continue;
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return ldci4.GetLdcI4Value();
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}
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throw new ApplicationException("Could not find magic1");
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}
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static int FindMagic2(MethodDef method) {
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var instrs = method.Body.Instructions;
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for (int i = 0; i < instrs.Count - 2; i++) {
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var ldloc = instrs[i];
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if (!ldloc.IsLdloc())
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continue;
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var ldci4 = instrs[i + 1];
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if (!ldci4.IsLdcI4())
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continue;
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if (instrs[i + 2].OpCode.Code != Code.Xor)
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continue;
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return ldci4.GetLdcI4Value();
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}
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throw new ApplicationException("Could not find magic2");
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}
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static int FindMagic3(MethodDef method) {
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var instrs = method.Body.Instructions;
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for (int i = 0; i < instrs.Count - 2; i++) {
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var ldarg = instrs[i];
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if (!ldarg.IsLdarg() || ldarg.GetParameterIndex() != 2)
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continue;
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var ldci4 = instrs[i + 1];
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if (!ldci4.IsLdcI4())
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continue;
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if (instrs[i + 2].OpCode.Code != Code.Xor)
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continue;
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return ldci4.GetLdcI4Value();
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}
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throw new ApplicationException("Could not find magic3");
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}
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public string Decrypt(MethodDef method, int magic1, int magic2, int magic3) {
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var info = stringEncrypterInfos.Find(method);
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return info.Decrypt(magic1, magic2, magic3);
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}
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}
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}
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