290 lines
8.7 KiB
C#
290 lines
8.7 KiB
C#
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/*
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Copyright (C) 2011 de4dot@gmail.com
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This file is part of de4dot.
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de4dot is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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de4dot is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with de4dot. If not, see <http://www.gnu.org/licenses/>.
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*/
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using System;
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using System.Collections.Generic;
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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.deobfuscators.SmartAssembly {
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class StringDecrypterInfo {
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ModuleDefinition module;
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ResourceDecrypter resourceDecrypter;
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TypeDefinition stringsEncodingClass;
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EmbeddedResource stringsResource;
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int stringOffset;
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TypeDefinition simpleZipType;
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MethodDefinition stringDecrypterMethod;
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public TypeDefinition GetStringDelegate { get; set; }
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public TypeDefinition StringsType { get; set; }
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public MethodDefinition CreateStringDelegateMethod { get; set; }
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public TypeDefinition StringsEncodingClass {
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get { return stringsEncodingClass; }
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}
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public bool CanDecrypt {
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get { return resourceDecrypter == null || resourceDecrypter.CanDecrypt; }
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}
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public TypeDefinition SimpleZipType {
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get { return simpleZipType; }
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}
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public EmbeddedResource StringsResource {
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get { return stringsResource; }
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}
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public int StringOffset {
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get { return stringOffset; }
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}
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public bool StringsEncrypted {
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get { return simpleZipType != null; }
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}
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public MethodDefinition StringDecrypterMethod {
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get { return stringDecrypterMethod; }
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}
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public StringDecrypterInfo(ModuleDefinition module, TypeDefinition stringsEncodingClass) {
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this.module = module;
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this.stringsEncodingClass = stringsEncodingClass;
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}
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public bool init(IDeobfuscator deob, ISimpleDeobfuscator simpleDeobfuscator) {
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var cctor = DotNetUtils.getMethod(stringsEncodingClass, ".cctor");
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if (cctor == null)
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throw new ApplicationException("Could not find .cctor");
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simpleDeobfuscator.deobfuscate(cctor);
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stringsResource = findStringResource(cctor);
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if (stringsResource == null) {
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simpleDeobfuscator.decryptStrings(cctor, deob);
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stringsResource = findStringResource(cctor);
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if (stringsResource == null)
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return false;
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}
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var offsetVal = findOffsetValue(cctor);
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if (offsetVal == null)
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throw new ApplicationException("Could not find string offset");
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stringOffset = offsetVal.Value;
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if (!findDecrypterMethod())
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throw new ApplicationException("Could not find string decrypter method");
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simpleZipType = findSimpleZipType(cctor);
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if (simpleZipType != null)
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resourceDecrypter = new ResourceDecrypter(new ResourceDecrypterInfo(module, simpleZipType, simpleDeobfuscator));
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return true;
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}
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public byte[] decrypt() {
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if (!CanDecrypt)
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throw new ApplicationException("Can't decrypt strings");
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return resourceDecrypter.decrypt(stringsResource);
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}
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// Find the embedded resource where all the strings are encrypted
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EmbeddedResource findStringResource(MethodDefinition method) {
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foreach (var ldstr in method.Body.Instructions) {
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if (ldstr.OpCode.Code != Code.Ldstr)
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continue;
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var s = ldstr.Operand as string;
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if (s == null)
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continue;
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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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// Find the string decrypter string offset value or null if none found
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int? findOffsetValue(MethodDefinition method) {
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var offsetField = findOffsetField(method);
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if (offsetField == null)
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return null;
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return findOffsetValue(method, offsetField);
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}
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FieldReference findOffsetField(MethodDefinition method) {
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var instructions = method.Body.Instructions;
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for (int i = 0; i <= instructions.Count - 2; i++) {
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var ldsfld = instructions[i];
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if (ldsfld.OpCode.Code != Code.Ldsfld)
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continue;
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var field = ldsfld.Operand as FieldReference;
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if (field == null || field.FieldType.FullName != "System.String")
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continue;
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if (!MemberReferenceHelper.compareTypes(stringsEncodingClass, field.DeclaringType))
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continue;
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var call = instructions[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 MethodReference;
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if (!DotNetUtils.isMethod(calledMethod, "System.Int32", "(System.String)"))
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continue;
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return field;
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}
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return null;
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}
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int? findOffsetValue(MethodDefinition method, FieldReference offsetField) {
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var instructions = method.Body.Instructions;
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for (int i = 0; i <= instructions.Count - 2; i++) {
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var ldstr = instructions[i];
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if (ldstr.OpCode.Code != Code.Ldstr)
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continue;
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var stringVal = ldstr.Operand as string;
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if (stringVal == null)
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continue;
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var stsfld = instructions[i + 1];
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if (stsfld.OpCode.Code != Code.Stsfld)
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continue;
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var field = stsfld.Operand as FieldReference;
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if (field == null || !MemberReferenceHelper.compareFieldReference(offsetField, field))
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continue;
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int value;
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if (!int.TryParse(stringVal, System.Globalization.NumberStyles.Integer, null, out value))
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continue;
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return value;
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}
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return null;
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}
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bool findDecrypterMethod() {
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var methods = new List<MethodDefinition>(DotNetUtils.findMethods(stringsEncodingClass.Methods, "System.String", new string[] { "System.Int32" }));
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if (methods.Count != 1)
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return false;
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stringDecrypterMethod = methods[0];
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return true;
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}
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// Find SmartAssembly.Zip.SimpleZip, which is the class that decrypts and inflates
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// data in the resources.
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TypeDefinition findSimpleZipType(MethodDefinition method) {
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var instructions = method.Body.Instructions;
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for (int i = 0; i <= instructions.Count - 2; i++) {
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var call = instructions[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 (!DotNetUtils.isMethod(calledMethod, "System.Byte[]", "(System.Byte[])"))
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continue;
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var stsfld = instructions[i + 1];
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if (stsfld.OpCode.Code != Code.Stsfld)
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continue;
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var field = stsfld.Operand as FieldReference;
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if (field == null || field.FieldType.FullName != "System.Byte[]")
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continue;
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if (!MemberReferenceHelper.compareTypes(stringsEncodingClass, field.DeclaringType))
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continue;
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var type = DotNetUtils.getType(module, calledMethod.DeclaringType);
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if (type == null)
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continue;
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return type;
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}
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return null;
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}
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public IEnumerable<FieldDefinition> getAllStringDelegateFields() {
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foreach (var type in module.GetTypes()) {
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foreach (var field in type.Fields) {
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if (field.FieldType == GetStringDelegate)
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yield return field;
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}
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}
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}
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public void removeInitCode(Blocks blocks) {
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if (CreateStringDelegateMethod == null)
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return;
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if (CreateStringDelegateMethod.Parameters.Count != 0)
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removeInitCode_v2(blocks);
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else
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removeInitCode_v1(blocks);
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}
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void removeInitCode_v1(Blocks blocks) {
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foreach (var block in blocks.MethodBlocks.getAllBlocks()) {
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var instructions = block.Instructions;
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for (int i = 0; i < instructions.Count; i++) {
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var call = instructions[i];
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if (call.OpCode != OpCodes.Call)
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continue;
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var method = call.Operand as MethodReference;
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if (!MemberReferenceHelper.compareMethodReferenceAndDeclaringType(method, CreateStringDelegateMethod))
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continue;
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block.remove(i, 1);
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break;
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}
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}
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}
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void removeInitCode_v2(Blocks blocks) {
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foreach (var block in blocks.MethodBlocks.getAllBlocks()) {
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var instructions = block.Instructions;
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for (int i = 0; i <= instructions.Count - 3; i++) {
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var ldtoken = instructions[i];
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if (ldtoken.OpCode != OpCodes.Ldtoken)
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continue;
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if (!MemberReferenceHelper.compareTypes(blocks.Method.DeclaringType, ldtoken.Operand as TypeReference))
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continue;
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var call1 = instructions[i + 1];
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if (call1.OpCode != OpCodes.Call)
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continue;
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var method1 = call1.Operand as MethodReference;
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if (method1 == null || method1.ToString() != "System.Type System.Type::GetTypeFromHandle(System.RuntimeTypeHandle)")
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continue;
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var call2 = instructions[i + 2];
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if (call2.OpCode != OpCodes.Call)
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continue;
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var method2 = call2.Operand as MethodReference;
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if (!MemberReferenceHelper.compareMethodReferenceAndDeclaringType(method2, CreateStringDelegateMethod))
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continue;
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block.remove(i, 3);
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break;
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}
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}
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}
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}
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}
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