441 lines
11 KiB
C#
441 lines
11 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.DotNet;
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using dnlib.DotNet.Emit;
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using de4dot.blocks;
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namespace de4dot.code.deobfuscators.Rummage {
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class StringDecrypter {
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ModuleDefMD module;
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FieldDefAndDeclaringTypeDict<StringInfo> stringInfos = new FieldDefAndDeclaringTypeDict<StringInfo>();
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IDecrypter decrypter;
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interface IDecrypter {
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RummageVersion Version { get; }
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MethodDef Method { get; }
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void Initialize();
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string Decrypt(int stringId);
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}
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abstract class DecrypterBaseV11 : IDecrypter {
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RummageVersion version;
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MethodDef decrypterMethod;
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protected int fileDispl;
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protected BinaryReader reader;
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protected uint[] key;
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public RummageVersion Version {
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get { return version; }
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}
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public MethodDef Method {
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get { return decrypterMethod; }
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}
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protected DecrypterBaseV11(RummageVersion version, MethodDef decrypterMethod, int fileDispl) {
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this.version = version;
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this.decrypterMethod = decrypterMethod;
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this.fileDispl = fileDispl;
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}
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public void Initialize() {
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reader = new BinaryReader(new FileStream(decrypterMethod.DeclaringType.Module.Location, FileMode.Open, FileAccess.Read, FileShare.Read));
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InitializeImpl();
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}
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protected abstract void InitializeImpl();
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protected static MethodDef FindDecrypterMethod(TypeDef type) {
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MethodDef cctor = null, decrypterMethod = null;
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foreach (var method in type.Methods) {
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if (!method.IsStatic || method.Body == null)
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return null;
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if (method.Name == ".cctor")
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cctor = method;
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else if (DotNetUtils.IsMethod(method, "System.String", "(System.Int32)"))
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decrypterMethod = method;
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else
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return null;
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}
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if (cctor == null || decrypterMethod == null)
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return null;
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return decrypterMethod;
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}
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public abstract string Decrypt(int stringId);
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protected string DecryptInternal(int stringId) {
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uint v0 = reader.ReadUInt32();
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uint v1 = reader.ReadUInt32();
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DeobUtils.XteaDecrypt(ref v0, ref v1, key, 32);
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int utf8Length = (int)v0;
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var decrypted = new uint[(utf8Length + 11) / 8 * 2 - 1];
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decrypted[0] = v1;
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for (int i = 1; i + 1 < decrypted.Length; i += 2) {
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v0 = reader.ReadUInt32();
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v1 = reader.ReadUInt32();
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DeobUtils.XteaDecrypt(ref v0, ref v1, key, 32);
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decrypted[i] = v0;
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decrypted[i + 1] = v1;
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}
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var utf8 = new byte[utf8Length];
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Buffer.BlockCopy(decrypted, 0, utf8, 0, utf8.Length);
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return Encoding.UTF8.GetString(utf8);
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}
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}
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class DecrypterV11 : DecrypterBaseV11 {
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DecrypterV11(MethodDef decrypterMethod, int fileDispl)
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: base(RummageVersion.V1_1_445, decrypterMethod, fileDispl) {
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}
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public static DecrypterV11 Create(MethodDef cctor) {
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var method = CheckType(cctor);
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if (method == null)
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return null;
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int fileDispl;
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if (!GetDispl(method, out fileDispl))
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return null;
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return new DecrypterV11(method, fileDispl);
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}
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static readonly string[] requiredFields = new string[] {
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"System.UInt32[]",
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};
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static readonly string[] requiredLocals = new string[] {
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"System.Byte[]",
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"System.Int32",
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"System.IO.FileStream",
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};
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static MethodDef CheckType(MethodDef cctor) {
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var type = cctor.DeclaringType;
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if (!new FieldTypes(type).Exactly(requiredFields))
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return null;
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if (!new LocalTypes(cctor).All(requiredLocals))
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return null;
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return FindDecrypterMethod(type);
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}
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static bool GetDispl(MethodDef method, out int displ) {
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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 mul = instrs[i];
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if (mul.OpCode.Code != Code.Mul)
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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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var sub = instrs[i + 2];
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if (sub.OpCode.Code != Code.Sub)
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continue;
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displ = ldci4.GetLdcI4Value();
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return true;
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}
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displ = 0;
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return false;
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}
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protected override void InitializeImpl() {
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InitKey();
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}
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void InitKey() {
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reader.BaseStream.Position = reader.BaseStream.Length - 48;
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key = new uint[4];
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for (int i = 0; i < key.Length; i++)
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key[i] = reader.ReadUInt32();
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}
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public override string Decrypt(int stringId) {
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reader.BaseStream.Position = reader.BaseStream.Length + (stringId * 4 - fileDispl);
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return DecryptInternal(stringId);
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}
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}
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class DecrypterV21 : DecrypterBaseV11 {
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long baseOffs;
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public DecrypterV21(MethodDef decrypterMethod, int fileDispl)
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: base(RummageVersion.V2_1_729, decrypterMethod, fileDispl) {
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}
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public static DecrypterV21 Create(MethodDef cctor) {
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var method = CheckType(cctor);
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if (method == null)
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return null;
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int fileDispl;
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if (!GetDispl(method, out fileDispl))
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return null;
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return new DecrypterV21(method, fileDispl);
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}
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static readonly string[] requiredFields = new string[] {
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"System.UInt32[]",
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"System.Int64",
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};
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static readonly string[] requiredLocals = new string[] {
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"System.Byte[]",
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"System.Int32",
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"System.IO.FileStream",
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};
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static MethodDef CheckType(MethodDef cctor) {
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var type = cctor.DeclaringType;
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if (!new FieldTypes(type).Exactly(requiredFields))
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return null;
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if (!new LocalTypes(cctor).All(requiredLocals))
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return null;
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return FindDecrypterMethod(type);
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}
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static bool GetDispl(MethodDef method, out int displ) {
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var instrs = method.Body.Instructions;
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for (int i = 0; i < instrs.Count - 6; i++) {
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var ldci4_1 = instrs[i];
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if (!ldci4_1.IsLdcI4() || ldci4_1.GetLdcI4Value() != 4)
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continue;
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if (instrs[i + 1].OpCode.Code != Code.Mul)
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continue;
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if (instrs[i + 2].OpCode.Code != Code.Conv_I8)
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continue;
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if (instrs[i + 3].OpCode.Code != Code.Add)
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continue;
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var ldci4 = instrs[i + 4];
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if (!ldci4.IsLdcI4())
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continue;
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if (instrs[i + 5].OpCode.Code != Code.Conv_I8)
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continue;
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if (instrs[i + 6].OpCode.Code != Code.Sub)
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continue;
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displ = ldci4.GetLdcI4Value();
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return true;
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}
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displ = 0;
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return false;
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}
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static readonly byte[] magic = new byte[32] {
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0xC9, 0x76, 0xC3, 0x0D, 0xE2, 0x83, 0x72, 0xE4,
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0xD5, 0xC7, 0x35, 0xF8, 0x86, 0xD0, 0x60, 0x69,
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0xEE, 0xE1, 0x4C, 0x5E, 0x07, 0xA1, 0xC1, 0xFE,
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0x61, 0xE3, 0xAA, 0xBC, 0xE4, 0xB1, 0xF0, 0x92,
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};
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protected override void InitializeImpl() {
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baseOffs = InitializeBaseOffs();
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InitKey();
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}
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void InitKey() {
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reader.BaseStream.Position = baseOffs - 16;
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key = new uint[4];
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for (int i = 0; i < key.Length; i++)
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key[i] = reader.ReadUInt32();
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}
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long InitializeBaseOffs() {
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byte[] buf = new byte[0x1000]; // Must be 4096 bytes
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reader.BaseStream.Position = reader.BaseStream.Length - buf.Length;
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while (true) {
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if (reader.Read(buf, 0, buf.Length) != buf.Length)
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throw new ApplicationException("Could not read");
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for (int bi = buf.Length - 1; bi > magic.Length; ) {
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int mi = magic.Length - 1;
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if (buf[bi--] != magic[mi--] ||
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buf[bi] != magic[mi--])
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continue;
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while (true) {
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if (buf[--bi] != magic[mi--])
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break;
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if (mi == -1)
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return reader.BaseStream.Position - buf.Length + bi;
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}
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}
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reader.BaseStream.Position -= buf.Length * 2 - 0x20;
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}
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}
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public override string Decrypt(int stringId) {
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reader.BaseStream.Position = baseOffs + stringId * 4 - fileDispl;
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return DecryptInternal(stringId);
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}
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}
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class StringInfo {
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public readonly FieldDef field;
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public readonly int stringId;
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public string decrypted;
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public StringInfo(FieldDef field, int stringId) {
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this.field = field;
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this.stringId = stringId;
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}
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public override string ToString() {
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if (decrypted != null)
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return string.Format("{0:X8} - {1}", stringId, Utils.ToCsharpString(decrypted));
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return string.Format("{0:X8}", stringId);
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}
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}
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public RummageVersion Version {
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get { return decrypter == null ? RummageVersion.Unknown : decrypter.Version; }
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}
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public TypeDef Type {
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get { return decrypter != null ? decrypter.Method.DeclaringType : null; }
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}
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public IEnumerable<TypeDef> OtherTypes {
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get {
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var list = new List<TypeDef>(stringInfos.Count);
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foreach (var info in stringInfos.GetValues())
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list.Add(info.field.DeclaringType);
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return list;
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}
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}
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public bool Detected {
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get { return decrypter != null; }
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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.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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decrypter = DecrypterV11.Create(cctor);
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if (decrypter != null)
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break;
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decrypter = DecrypterV21.Create(cctor);
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if (decrypter != null)
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break;
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}
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}
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public void Initialize() {
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if (decrypter == null)
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return;
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decrypter.Initialize();
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foreach (var type in module.Types)
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InitType(type);
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}
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void InitType(TypeDef type) {
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var cctor = type.FindStaticConstructor();
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if (cctor == null)
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return;
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var info = GetStringInfo(cctor);
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if (info == null)
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return;
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stringInfos.Add(info.field, info);
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}
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StringInfo GetStringInfo(MethodDef method) {
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if (method == null || method.Body == null)
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return null;
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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 ldci4 = instrs[i];
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if (!ldci4.IsLdcI4())
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continue;
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int stringId = ldci4.GetLdcI4Value();
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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 IMethod;
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if (!MethodEqualityComparer.CompareDeclaringTypes.Equals(decrypter.Method, calledMethod))
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continue;
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var stsfld = instrs[i + 2];
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if (stsfld.OpCode.Code != Code.Stsfld)
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continue;
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var field = stsfld.Operand as FieldDef;
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if (field == null)
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continue;
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return new StringInfo(field, stringId);
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}
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return null;
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}
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public void Deobfuscate(Blocks blocks) {
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if (decrypter == null)
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return;
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foreach (var block in blocks.MethodBlocks.GetAllBlocks()) {
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var instrs = block.Instructions;
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for (int i = 0; i < instrs.Count; i++) {
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var instr = instrs[i];
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if (instr.OpCode.Code != Code.Ldsfld)
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continue;
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var field = instr.Operand as IField;
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if (field == null)
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continue;
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var info = stringInfos.Find(field);
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if (info == null)
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continue;
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var decrypted = Decrypt(info);
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instrs[i] = new Instr(OpCodes.Ldstr.ToInstruction(decrypted));
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Logger.v("Decrypted string: {0}", Utils.ToCsharpString(decrypted));
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}
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}
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}
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string Decrypt(StringInfo info) {
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if (info.decrypted == null)
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info.decrypted = decrypter.Decrypt(info.stringId);
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return info.decrypted;
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}
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}
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}
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