476 lines
14 KiB
C#
476 lines
14 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.IO;
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using System.Collections.Generic;
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using System.Security.Cryptography;
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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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using de4dot.blocks.cflow;
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namespace de4dot.code.deobfuscators.dotNET_Reactor.v4 {
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enum DnrDecrypterType {
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Unknown,
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V1,
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V2,
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}
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class EncryptedResource {
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ModuleDefMD module;
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MethodDef resourceDecrypterMethod;
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EmbeddedResource encryptedDataResource;
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IDecrypter decrypter;
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public DnrDecrypterType DecrypterTypeVersion {
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get { return decrypter == null ? DnrDecrypterType.Unknown : decrypter.DecrypterType; }
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}
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public TypeDef Type {
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get { return resourceDecrypterMethod == null ? null : resourceDecrypterMethod.DeclaringType; }
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}
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public MethodDef Method {
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get { return resourceDecrypterMethod; }
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set { resourceDecrypterMethod = value; }
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}
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public EmbeddedResource Resource {
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get { return encryptedDataResource; }
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}
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public bool FoundResource {
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get { return encryptedDataResource != null; }
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}
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public EncryptedResource(ModuleDefMD module) {
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this.module = module;
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}
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public EncryptedResource(ModuleDefMD module, EncryptedResource oldOne) {
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this.module = module;
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resourceDecrypterMethod = Lookup(oldOne.resourceDecrypterMethod, "Could not find resource decrypter method");
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if (oldOne.encryptedDataResource != null)
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encryptedDataResource = DotNetUtils.GetResource(module, oldOne.encryptedDataResource.Name.String) as EmbeddedResource;
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this.decrypter = oldOne.decrypter;
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if (encryptedDataResource == null && oldOne.encryptedDataResource != null)
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throw new ApplicationException("Could not initialize EncryptedResource");
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}
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T Lookup<T>(T def, string errorMessage) where T : class, ICodedToken {
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return DeobUtils.Lookup(module, def, errorMessage);
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}
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public bool CouldBeResourceDecrypter(MethodDef method, IList<string> additionalTypes) {
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return CouldBeResourceDecrypter(method, additionalTypes, true);
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}
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public bool CouldBeResourceDecrypter(MethodDef method, IList<string> additionalTypes, bool checkResource) {
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if (GetDecrypterType(method, additionalTypes) == DnrDecrypterType.Unknown)
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return false;
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if (checkResource && FindMethodsDecrypterResource(method) == null)
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return false;
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return true;
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}
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public DnrDecrypterType GuessDecrypterType() {
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return GetDecrypterType(resourceDecrypterMethod, null);
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}
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static DnrDecrypterType GetDecrypterType(MethodDef method, IList<string> additionalTypes) {
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if (method == null || !method.IsStatic || method.Body == null)
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return DnrDecrypterType.Unknown;
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if (additionalTypes == null)
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additionalTypes = new string[0];
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var localTypes = new LocalTypes(method);
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if (DecrypterV1.CouldBeResourceDecrypter(method, localTypes, additionalTypes))
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return DnrDecrypterType.V1;
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else if (DecrypterV2.CouldBeResourceDecrypter(method, localTypes, additionalTypes))
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return DnrDecrypterType.V2;
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return DnrDecrypterType.Unknown;
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}
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public void Initialize(ISimpleDeobfuscator simpleDeobfuscator) {
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if (resourceDecrypterMethod == null)
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return;
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simpleDeobfuscator.Deobfuscate(resourceDecrypterMethod);
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encryptedDataResource = FindMethodsDecrypterResource(resourceDecrypterMethod);
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if (encryptedDataResource == null)
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return;
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var key = ArrayFinder.GetInitializedByteArray(resourceDecrypterMethod, 32);
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if (key == null)
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throw new ApplicationException("Could not find resource decrypter key");
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var iv = ArrayFinder.GetInitializedByteArray(resourceDecrypterMethod, 16);
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if (iv == null)
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throw new ApplicationException("Could not find resource decrypter IV");
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if (NeedReverse())
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Array.Reverse(iv); // DNR 4.5.0.0
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if (UsesPublicKeyToken()) {
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var publicKeyToken = module.Assembly.PublicKeyToken;
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if (publicKeyToken != null && publicKeyToken.Data.Length > 0) {
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for (int i = 0; i < 8; i++)
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iv[i * 2 + 1] = publicKeyToken.Data[i];
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}
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}
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var decrypterType = GetDecrypterType(resourceDecrypterMethod, new string[0]);
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switch (decrypterType) {
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case DnrDecrypterType.V1: decrypter = new DecrypterV1(iv, key); break;
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case DnrDecrypterType.V2: decrypter = new DecrypterV2(iv, key, resourceDecrypterMethod); break;
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default: throw new ApplicationException("Unknown decrypter type");
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}
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}
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static int[] pktIndexes = new int[16] { 1, 0, 3, 1, 5, 2, 7, 3, 9, 4, 11, 5, 13, 6, 15, 7 };
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bool UsesPublicKeyToken() {
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int pktIndex = 0;
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foreach (var instr in resourceDecrypterMethod.Body.Instructions) {
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if (instr.OpCode.FlowControl != FlowControl.Next) {
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pktIndex = 0;
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continue;
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}
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if (!instr.IsLdcI4())
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continue;
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int val = instr.GetLdcI4Value();
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if (val != pktIndexes[pktIndex++]) {
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pktIndex = 0;
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continue;
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}
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if (pktIndex >= pktIndexes.Length)
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return true;
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}
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return false;
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}
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bool NeedReverse() {
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return DotNetUtils.CallsMethod(resourceDecrypterMethod, "System.Void System.Array::Reverse(System.Array)");
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}
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EmbeddedResource FindMethodsDecrypterResource(MethodDef method) {
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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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return null;
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}
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interface IDecrypter {
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DnrDecrypterType DecrypterType { get; }
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byte[] Decrypt(EmbeddedResource resource);
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byte[] Encrypt(byte[] data);
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}
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class DecrypterV1 : IDecrypter {
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readonly byte[] key, iv;
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public DnrDecrypterType DecrypterType {
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get { return DnrDecrypterType.V1; }
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}
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public DecrypterV1(byte[] iv, byte[] key) {
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this.iv = iv;
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this.key = key;
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}
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public static bool CouldBeResourceDecrypter(MethodDef method, LocalTypes localTypes, IList<string> additionalTypes) {
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var requiredTypes = new List<string> {
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"System.Byte[]",
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"System.IO.BinaryReader",
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"System.IO.MemoryStream",
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"System.Security.Cryptography.CryptoStream",
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"System.Security.Cryptography.ICryptoTransform",
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};
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requiredTypes.AddRange(additionalTypes);
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if (!localTypes.All(requiredTypes))
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return false;
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if (DotNetUtils.GetMethod(method.DeclaringType, "System.Security.Cryptography.SymmetricAlgorithm", "()") != null)
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if (localTypes.Exists("System.UInt64"))
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return false;
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if (!localTypes.Exists("System.Security.Cryptography.RijndaelManaged") &&
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!localTypes.Exists("System.Security.Cryptography.AesManaged") &&
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!localTypes.Exists("System.Security.Cryptography.SymmetricAlgorithm"))
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return false;
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return true;
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}
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public byte[] Decrypt(EmbeddedResource resource) {
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return DeobUtils.AesDecrypt(resource.GetResourceData(), key, iv);
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}
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public byte[] Encrypt(byte[] data) {
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using (var aes = new RijndaelManaged { Mode = CipherMode.CBC }) {
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using (var transform = aes.CreateEncryptor(key, iv)) {
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return transform.TransformFinalBlock(data, 0, data.Length);
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}
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}
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}
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}
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class DecrypterV2 : IDecrypter {
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readonly byte[] key, iv;
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readonly MethodDef method;
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List<Instruction> instructions;
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readonly List<Local> locals;
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readonly InstructionEmulator instrEmulator = new InstructionEmulator();
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Local emuLocal;
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public DnrDecrypterType DecrypterType {
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get { return DnrDecrypterType.V2; }
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}
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public DecrypterV2(byte[] iv, byte[] key, MethodDef method) {
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this.iv = iv;
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this.key = key;
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this.method = method;
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this.locals = new List<Local>(method.Body.Variables);
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if (!Initialize())
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throw new ApplicationException("Could not initialize decrypter");
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}
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public static bool CouldBeResourceDecrypter(MethodDef method, LocalTypes localTypes, IList<string> additionalTypes) {
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var requiredTypes = new List<string> {
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"System.UInt32",
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"System.String",
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"System.Int32",
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"System.Byte[]",
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"System.IO.BinaryReader",
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};
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requiredTypes.AddRange(additionalTypes);
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if (!localTypes.All(requiredTypes))
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return false;
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return true;
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}
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bool Initialize() {
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for (int i = 0; i < iv.Length; i++)
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key[i] ^= iv[i];
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var origInstrs = method.Body.Instructions;
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int emuEndIndex;
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int emuStartIndex;
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if (!Find(origInstrs, out emuStartIndex, out emuEndIndex, out emuLocal)) {
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if (!FindStartEnd(origInstrs, out emuStartIndex, out emuEndIndex, out emuLocal))
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return false;
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}
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int count = emuEndIndex - emuStartIndex + 1;
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instructions = new List<Instruction>(count);
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for (int i = 0; i < count; i++)
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instructions.Add(origInstrs[emuStartIndex + i].Clone());
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return true;
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}
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bool Find(IList<Instruction> instrs, out int startIndex, out int endIndex, out Local tmpLocal) {
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int emuStartIndex;
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startIndex = 0;
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endIndex = 0;
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tmpLocal = null;
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if (!FindStart(instrs, out emuStartIndex, out emuLocal))
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return false;
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int emuEndIndex;
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if (!FindEnd(instrs, emuStartIndex, out emuEndIndex))
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return false;
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startIndex = emuStartIndex;
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endIndex = emuEndIndex;
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tmpLocal = emuLocal;
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return true;
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}
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bool FindStartEnd(IList<Instruction> instrs, out int startIndex, out int endIndex, out Local tmpLocal) {
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for (int i = 0; i + 8 < instrs.Count; i++) {
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if (instrs[i].OpCode.Code != Code.Conv_R_Un)
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continue;
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if (instrs[i + 1].OpCode.Code != Code.Conv_R8)
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continue;
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if (instrs[i + 2].OpCode.Code != Code.Conv_U4)
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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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int newEndIndex = i + 3;
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int newStartIndex = -1;
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for (int x = newEndIndex; x > 0; x--)
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if (instrs[x].OpCode.FlowControl != FlowControl.Next) {
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newStartIndex = x + 1;
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break;
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}
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if (newStartIndex < 0)
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continue;
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endIndex = newEndIndex;
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startIndex = newStartIndex;
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tmpLocal = CheckLocal(instrs[startIndex], true);
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return true;
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}
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endIndex = 0;
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startIndex = 0;
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tmpLocal = null;
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return false;
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}
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bool FindStart(IList<Instruction> instrs, out int startIndex, out Local tmpLocal) {
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for (int i = 0; i + 8 < instrs.Count; i++) {
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if (instrs[i].OpCode.Code != Code.Conv_U)
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continue;
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if (instrs[i + 1].OpCode.Code != Code.Ldelem_U1)
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continue;
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if (instrs[i + 2].OpCode.Code != Code.Or)
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continue;
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if (CheckLocal(instrs[i + 3], false) == null)
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continue;
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Local local;
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if ((local = CheckLocal(instrs[i + 4], true)) == null)
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continue;
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if (CheckLocal(instrs[i + 5], true) == null)
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continue;
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if (instrs[i + 6].OpCode.Code != Code.Add)
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continue;
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if (CheckLocal(instrs[i + 7], false) != local)
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continue;
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var instr = instrs[i + 8];
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int newStartIndex = i + 8;
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if (instr.IsBr()) {
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instr = instr.Operand as Instruction;
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newStartIndex = instrs.IndexOf(instr);
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}
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if (newStartIndex < 0 || instr == null)
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continue;
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if (CheckLocal(instr, true) != local)
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continue;
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startIndex = newStartIndex;
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tmpLocal = local;
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return true;
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}
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startIndex = 0;
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tmpLocal = null;
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return false;
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}
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bool FindEnd(IList<Instruction> instrs, int startIndex, out int endIndex) {
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for (int i = startIndex; i < instrs.Count; i++) {
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var instr = instrs[i];
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if (instr.OpCode.FlowControl != FlowControl.Next)
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break;
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if (instr.IsStloc() && instr.GetLocal(locals) == emuLocal) {
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endIndex = i - 1;
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return true;
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}
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}
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endIndex = 0;
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return false;
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}
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Local CheckLocal(Instruction instr, bool isLdloc) {
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if (isLdloc && !instr.IsLdloc())
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return null;
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else if (!isLdloc && !instr.IsStloc())
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return null;
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return instr.GetLocal(locals);
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}
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public byte[] Decrypt(EmbeddedResource resource) {
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var encrypted = resource.GetResourceData();
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var decrypted = new byte[encrypted.Length];
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uint sum = 0;
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for (int i = 0; i < encrypted.Length; i += 4) {
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sum = CalculateMagic(sum + ReadUInt32(key, i % key.Length));
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WriteUInt32(decrypted, i, sum ^ ReadUInt32(encrypted, i));
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}
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return decrypted;
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}
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uint CalculateMagic(uint input) {
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instrEmulator.Initialize(method, method.Parameters, locals, method.Body.InitLocals, false);
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instrEmulator.SetLocal(emuLocal, new Int32Value((int)input));
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foreach (var instr in instructions)
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instrEmulator.Emulate(instr);
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var tos = instrEmulator.Pop() as Int32Value;
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if (tos == null || !tos.AllBitsValid())
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throw new ApplicationException("Couldn't calculate magic value");
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return (uint)tos.Value;
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}
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static uint ReadUInt32(byte[] ary, int index) {
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int sizeLeft = ary.Length - index;
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if (sizeLeft >= 4)
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return BitConverter.ToUInt32(ary, index);
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switch (sizeLeft) {
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case 1: return ary[index];
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case 2: return (uint)(ary[index] | (ary[index + 1] << 8));
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case 3: return (uint)(ary[index] | (ary[index + 1] << 8) | (ary[index + 2] << 16));
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default: throw new ApplicationException("Can't read data");
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}
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}
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static void WriteUInt32(byte[] ary, int index, uint value) {
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int sizeLeft = ary.Length - index;
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if (sizeLeft >= 1)
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ary[index] = (byte)value;
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if (sizeLeft >= 2)
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ary[index + 1] = (byte)(value >> 8);
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if (sizeLeft >= 3)
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ary[index + 2] = (byte)(value >> 16);
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if (sizeLeft >= 4)
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ary[index + 3] = (byte)(value >> 24);
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}
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public byte[] Encrypt(byte[] data) {
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//TODO: Support re-encryption
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Logger.e("Re-encryption is not supported. Assembly will probably crash at runtime.");
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return (byte[])data.Clone();
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}
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}
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public byte[] Decrypt() {
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if (encryptedDataResource == null || decrypter == null)
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throw new ApplicationException("Can't decrypt resource");
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return decrypter.Decrypt(encryptedDataResource);
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}
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public byte[] Encrypt(byte[] data) {
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if (decrypter == null)
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throw new ApplicationException("Can't encrypt resource");
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return decrypter.Encrypt(data);
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}
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}
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}
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