265 lines
7.5 KiB
C#
265 lines
7.5 KiB
C#
/*
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Copyright (C) 2011-2012 de4dot@gmail.com
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This file is part of de4dot.
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de4dot is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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de4dot is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with de4dot. If not, see <http://www.gnu.org/licenses/>.
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*/
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using System.Collections.Generic;
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using System.IO;
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using Mono.Cecil;
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using Mono.Cecil.Cil;
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using de4dot.blocks;
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namespace de4dot.code.deobfuscators.Confuser {
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class ResourceDecrypter {
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ModuleDefinition module;
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ISimpleDeobfuscator simpleDeobfuscator;
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MethodDefinition handler;
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MethodDefinition installMethod;
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EmbeddedResource resource;
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Dictionary<FieldDefinition, bool> fields = new Dictionary<FieldDefinition, bool>();
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byte key0, key1;
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public IEnumerable<FieldDefinition> Fields {
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get { return fields.Keys; }
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}
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public MethodDefinition Handler {
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get { return handler; }
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}
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public bool Detected {
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get { return handler != null; }
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}
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public ResourceDecrypter(ModuleDefinition module, ISimpleDeobfuscator simpleDeobfuscator) {
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this.module = module;
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this.simpleDeobfuscator = simpleDeobfuscator;
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}
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public void find() {
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if (checkMethod(DotNetUtils.getModuleTypeCctor(module)))
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return;
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}
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bool checkMethod(MethodDefinition method) {
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if (method == null || method.Body == null)
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return false;
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if (!DotNetUtils.callsMethod(method, "System.Void System.AppDomain::add_ResourceResolve(System.ResolveEventHandler)"))
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return false;
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simpleDeobfuscator.deobfuscate(method, true);
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fields.Clear();
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var tmpHandler = getHandler(method);
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if (tmpHandler == null || tmpHandler.DeclaringType != method.DeclaringType)
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return false;
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simpleDeobfuscator.deobfuscate(tmpHandler, true);
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if (addFields(findFields(tmpHandler, method.DeclaringType)) != 1)
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return false;
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var tmpResource = findResource(tmpHandler);
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if (tmpResource == null)
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return false;
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if (!findKey0(tmpHandler, out key0))
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return false;
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if (!findKey1(tmpHandler, out key1))
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return false;
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handler = tmpHandler;
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resource = tmpResource;
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installMethod = method;
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return true;
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}
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static MethodDefinition getHandler(MethodDefinition 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 ldftn = instrs[i];
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if (ldftn.OpCode.Code != Code.Ldftn)
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continue;
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var handler = ldftn.Operand as MethodDefinition;
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if (handler == null)
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continue;
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var newobj = instrs[i + 1];
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if (newobj.OpCode.Code != Code.Newobj)
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continue;
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var callvirt = instrs[i + 2];
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if (callvirt.OpCode.Code != Code.Callvirt)
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continue;
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var calledMethod = callvirt.Operand as MethodReference;
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if (calledMethod == null)
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continue;
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if (calledMethod.FullName != "System.Void System.AppDomain::add_ResourceResolve(System.ResolveEventHandler)")
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continue;
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return handler;
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}
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return null;
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}
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int addFields(IEnumerable<FieldDefinition> moreFields) {
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int count = 0;
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foreach (var field in moreFields) {
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if (addField(field))
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count++;
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}
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return count;
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}
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bool addField(FieldDefinition field) {
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if (field == null)
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return false;
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if (fields.ContainsKey(field))
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return false;
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fields[field] = true;
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return true;
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}
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static IEnumerable<FieldDefinition> findFields(MethodDefinition method, TypeDefinition declaringType) {
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var fields = new List<FieldDefinition>();
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foreach (var instr in method.Body.Instructions) {
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var field = instr.Operand as FieldDefinition;
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if (field != null && field.DeclaringType == declaringType)
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fields.Add(field);
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}
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return fields;
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}
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EmbeddedResource findResource(MethodDefinition method) {
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return DotNetUtils.getResource(module, DotNetUtils.getCodeStrings(method)) as EmbeddedResource;
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}
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static bool findKey0(MethodDefinition method, out byte key0) {
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var instrs = method.Body.Instructions;
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for (int index = 0; index < instrs.Count; index++) {
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index = ConfuserUtils.findCallMethod(instrs, index, Code.Callvirt, "System.Int32 System.IO.Stream::Read(System.Byte[],System.Int32,System.Int32)");
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if (index < 0)
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break;
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if (index + 4 >= instrs.Count)
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break;
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index++;
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if (instrs[index++].OpCode.Code != Code.Pop)
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continue;
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var ldci4 = instrs[index++];
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if (!DotNetUtils.isLdcI4(ldci4))
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continue;
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if (instrs[index++].OpCode.Code != Code.Conv_U1)
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continue;
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if (!DotNetUtils.isStloc(instrs[index++]))
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continue;
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key0 = (byte)DotNetUtils.getLdcI4Value(ldci4);
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return true;
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}
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key0 = 0;
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return false;
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}
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static bool findKey1(MethodDefinition method, out byte key1) {
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var instrs = method.Body.Instructions;
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for (int i = 0; i < instrs.Count - 4; i++) {
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int index = i;
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if (!DotNetUtils.isLdloc(instrs[index++]))
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continue;
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var ldci4_1 = instrs[index++];
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if (!DotNetUtils.isLdcI4(ldci4_1))
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continue;
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if (instrs[index++].OpCode.Code != Code.Mul)
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continue;
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var ldci4_2 = instrs[index++];
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if (!DotNetUtils.isLdcI4(ldci4_2) || DotNetUtils.getLdcI4Value(ldci4_2) != 0x100)
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continue;
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if (instrs[index++].OpCode.Code != Code.Rem)
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continue;
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key1 = (byte)DotNetUtils.getLdcI4Value(ldci4_1);
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return true;
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}
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key1 = 0;
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return false;
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}
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public EmbeddedResource mergeResources() {
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if (resource == null)
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return null;
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DeobUtils.decryptAndAddResources(module, resource.Name, () => decryptResource());
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return resource;
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}
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byte[] decryptResource() {
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var encrypted = resource.GetResourceData();
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byte k = key0;
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for (int i = 0; i < encrypted.Length; i++) {
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encrypted[i] ^= k;
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k *= key1;
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}
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var reader = new BinaryReader(new MemoryStream(DeobUtils.inflate(encrypted, true)));
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return reader.ReadBytes(reader.ReadInt32());
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}
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public void deobfuscate(Blocks blocks) {
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if (blocks.Method != installMethod)
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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 - 4; i++) {
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var call = instrs[i];
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if (call.OpCode.Code != Code.Call)
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continue;
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var calledMethod = call.Operand as MethodReference;
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if (calledMethod == null || calledMethod.FullName != "System.AppDomain System.AppDomain::get_CurrentDomain()")
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continue;
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if (instrs[i + 1].OpCode.Code != Code.Ldnull)
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continue;
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var ldftn = instrs[i + 2];
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if (ldftn.OpCode.Code != Code.Ldftn)
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continue;
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if (ldftn.Operand != handler)
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continue;
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var newobj = instrs[i + 3];
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if (newobj.OpCode.Code != Code.Newobj)
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continue;
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var ctor = newobj.Operand as MethodReference;
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if (ctor == null || ctor.FullName != "System.Void System.ResolveEventHandler::.ctor(System.Object,System.IntPtr)")
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continue;
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var callvirt = instrs[i + 4];
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if (callvirt.OpCode.Code != Code.Callvirt)
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continue;
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calledMethod = callvirt.Operand as MethodReference;
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if (calledMethod == null || calledMethod.FullName != "System.Void System.AppDomain::add_ResourceResolve(System.ResolveEventHandler)")
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continue;
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block.remove(i, 5);
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return;
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}
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}
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}
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}
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}
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