270 lines
8.3 KiB
C#
270 lines
8.3 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;
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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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using de4dot.PE;
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namespace de4dot.code.deobfuscators.Confuser {
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class ProxyCallFixer : ProxyCallFixer2 {
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byte[] fileData;
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ISimpleDeobfuscator simpleDeobfuscator;
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MethodDefinitionAndDeclaringTypeDict<ProxyCreatorInfo> methodToInfo = new MethodDefinitionAndDeclaringTypeDict<ProxyCreatorInfo>();
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FieldDefinitionAndDeclaringTypeDict<MethodDefinition> fieldToMethod = new FieldDefinitionAndDeclaringTypeDict<MethodDefinition>();
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x86Emulator x86emu;
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enum ProxyCreatorType {
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None,
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CallOrCallvirt,
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Newobj,
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}
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class ProxyCreatorInfo {
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public readonly MethodDefinition creatorMethod;
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public readonly ProxyCreatorType proxyCreatorType;
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public uint? key;
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public MethodDefinition nativeMethod;
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public ushort callvirtChar;
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public ProxyCreatorInfo(MethodDefinition creatorMethod, ProxyCreatorType proxyCreatorType) {
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this.creatorMethod = creatorMethod;
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this.proxyCreatorType = proxyCreatorType;
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}
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}
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protected override bool ProxyCallIsObfuscated {
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get { return true; }
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}
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public override IEnumerable<Tuple<MethodDefinition, string>> OtherMethods {
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get {
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var list = new List<Tuple<MethodDefinition, string>>();
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foreach (var info in methodToInfo.getValues()) {
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list.Add(new Tuple<MethodDefinition, string> {
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Item1 = info.creatorMethod,
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Item2 = "Delegate creator method",
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});
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list.Add(new Tuple<MethodDefinition, string> {
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Item1 = info.nativeMethod,
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Item2 = "Calculate RID native method",
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});
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}
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return list;
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}
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}
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public ProxyCallFixer(ModuleDefinition module, byte[] fileData, ISimpleDeobfuscator simpleDeobfuscator)
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: base(module) {
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this.fileData = fileData;
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this.simpleDeobfuscator = simpleDeobfuscator;
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}
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protected override object checkCctor(TypeDefinition type, MethodDefinition cctor) {
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var instrs = cctor.Body.Instructions;
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object retVal = null;
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for (int i = 0; i < instrs.Count - 1; i++) {
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var ldtoken = instrs[i];
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if (ldtoken.OpCode.Code != Code.Ldtoken)
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continue;
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var field = ldtoken.Operand as FieldDefinition;
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if (field == null)
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continue;
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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 MethodDefinition;
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if (!isDelegateCreatorMethod(calledMethod))
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continue;
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fieldToMethod.add(field, calledMethod);
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retVal = this;
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}
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return retVal;
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}
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protected override void getCallInfo(object context, FieldDefinition field, out MethodReference calledMethod, out OpCode callOpcode) {
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var info = getProxyCreatorInfo(field);
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var sig = module.GetSignatureBlob(field);
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int len = sig.Length;
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uint magic = (uint)((sig[len - 2] << 24) | (sig[len - 3] << 16) | (sig[len - 5] << 8) | sig[len - 6]);
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uint rid = getRid(info, magic);
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int token = (sig[len - 7] << 24) | (int)rid;
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calledMethod = module.LookupToken(token) as MethodReference;
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callOpcode = getCallOpCode(info, field);
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}
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OpCode getCallOpCode(ProxyCreatorInfo info, FieldDefinition field) {
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switch (info.proxyCreatorType) {
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case ProxyCreatorType.CallOrCallvirt:
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if (field.Name.Length > 0 && field.Name[0] == info.callvirtChar)
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return OpCodes.Callvirt;
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return OpCodes.Call;
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case ProxyCreatorType.Newobj:
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return OpCodes.Newobj;
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default: throw new NotSupportedException();
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}
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}
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ProxyCreatorInfo getProxyCreatorInfo(FieldReference field) {
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return methodToInfo.find(fieldToMethod.find(field));
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}
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uint getRid(ProxyCreatorInfo info, uint magic) {
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if (info.key != null)
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return magic ^ info.key.Value;
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if (info.nativeMethod != null) {
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if (x86emu == null)
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x86emu = new x86Emulator(new PeImage(fileData));
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return x86emu.emulate((uint)info.nativeMethod.RVA, magic);
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}
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throw new NotImplementedException();
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}
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public void findDelegateCreator() {
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var type = DotNetUtils.getModuleType(module);
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if (type == null)
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return;
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foreach (var method in type.Methods) {
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if (!method.IsStatic || method.Body == null)
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continue;
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if (!DotNetUtils.isMethod(method, "System.Void", "(System.RuntimeFieldHandle)"))
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continue;
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var creatorType = getProxyCreatorType(method);
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if (creatorType == ProxyCreatorType.None)
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continue;
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methodToInfo.add(method, createProxyCreatorInfo(method, creatorType));
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setDelegateCreatorMethod(method);
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}
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}
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ProxyCreatorType getProxyCreatorType(MethodDefinition method) {
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foreach (var instr in method.Body.Instructions) {
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var field = instr.Operand as FieldReference;
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if (field == null)
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continue;
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switch (field.FullName) {
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case "System.Reflection.Emit.OpCode System.Reflection.Emit.OpCodes::Call":
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case "System.Reflection.Emit.OpCode System.Reflection.Emit.OpCodes::Callvirt":
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return ProxyCreatorType.CallOrCallvirt;
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case "System.Reflection.Emit.OpCode System.Reflection.Emit.OpCodes::Newobj":
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return ProxyCreatorType.Newobj;
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}
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}
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return ProxyCreatorType.None;
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}
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ProxyCreatorInfo createProxyCreatorInfo(MethodDefinition creatorMethod, ProxyCreatorType proxyCreatorType) {
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simpleDeobfuscator.deobfuscate(creatorMethod, true);
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var info = new ProxyCreatorInfo(creatorMethod, proxyCreatorType);
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if (!initializeKey(info))
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throw new NotSupportedException("Couldn't find decryption key");
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if (info.proxyCreatorType == ProxyCreatorType.CallOrCallvirt) {
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if (!initializeCallvirtChar(info))
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throw new ApplicationException("Couldn't find callvirt char");
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}
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return info;
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}
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bool initializeKey(ProxyCreatorInfo info) {
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var instrs = info.creatorMethod.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.Reflection.Module System.Reflection.MemberInfo::get_Module()");
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if (index < 0)
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break;
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uint key;
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if (getKey(instrs, index + 1, out key)) {
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info.key = key;
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return true;
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}
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var nativeMethod = getNativeMethod(instrs, index + 1);
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if (nativeMethod != null) {
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info.nativeMethod = nativeMethod;
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return true;
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}
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}
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return false;
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}
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static bool getKey(IList<Instruction> instrs, int index, out uint key) {
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key = 0;
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if (index + 2 >= instrs.Count)
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return false;
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if (!DotNetUtils.isLdloc(instrs[index++]))
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return false;
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var ldci4 = instrs[index++];
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if (!DotNetUtils.isLdcI4(ldci4))
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return false;
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if (instrs[index++].OpCode.Code != Code.Xor)
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return false;
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key = (uint)DotNetUtils.getLdcI4Value(ldci4);
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return true;
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}
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static MethodDefinition getNativeMethod(IList<Instruction> instrs, int index) {
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if (index + 1 >= instrs.Count)
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return null;
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if (!DotNetUtils.isLdloc(instrs[index++]))
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return null;
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var call = instrs[index++];
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if (call.OpCode.Code != Code.Call)
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return null;
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var calledMethod = call.Operand as MethodDefinition;
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if (calledMethod == null || calledMethod.Body != null || !calledMethod.IsNative)
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return null;
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return calledMethod;
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}
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bool initializeCallvirtChar(ProxyCreatorInfo info) {
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var instrs = info.creatorMethod.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.Char System.String::get_Chars(System.Int32)");
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if (index < 0)
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break;
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index++;
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if (index >= instrs.Count)
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break;
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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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info.callvirtChar = (ushort)DotNetUtils.getLdcI4Value(ldci4);
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return true;
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}
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return false;
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}
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}
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}
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