Strings and resources are decrypted
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dd13df28d6
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@ -61,6 +61,7 @@
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<Compile Include="deobfuscators\CryptoObfuscator\Deobfuscator.cs" />
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<Compile Include="deobfuscators\CryptoObfuscator\ResourceDecrypter.cs" />
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<Compile Include="deobfuscators\CryptoObfuscator\ResourceResolver.cs" />
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<Compile Include="deobfuscators\CryptoObfuscator\StringDecrypter.cs" />
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<Compile Include="deobfuscators\DeobfuscatorBase.cs" />
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<Compile Include="deobfuscators\DeobfuscatorInfoBase.cs" />
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<Compile Include="deobfuscators\DeobUtils.cs" />
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@ -58,6 +58,7 @@ namespace de4dot.deobfuscators.CryptoObfuscator {
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ResourceDecrypter resourceDecrypter;
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ResourceResolver resourceResolver;
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AssemblyResolver assemblyResolver;
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StringDecrypter stringDecrypter;
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internal class Options : OptionsBase {
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}
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@ -88,6 +89,8 @@ namespace de4dot.deobfuscators.CryptoObfuscator {
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val += 100;
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else if (foundObfuscatedSymbols)
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val += 10;
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if (stringDecrypter.Detected)
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val += 10;
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return val;
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}
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@ -102,6 +105,9 @@ namespace de4dot.deobfuscators.CryptoObfuscator {
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}
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if (checkCryptoObfuscator())
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foundObfuscatedSymbols = true;
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stringDecrypter = new StringDecrypter(module);
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stringDecrypter.detect();
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}
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void initializeVersion(TypeDefinition attr) {
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@ -140,9 +146,24 @@ namespace de4dot.deobfuscators.CryptoObfuscator {
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resourceResolver.find();
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assemblyResolver.find();
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decryptResources();
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stringDecrypter.init(resourceDecrypter);
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if (stringDecrypter.StringDecrypterMethod != null) {
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staticStringDecrypter.add(stringDecrypter.StringDecrypterMethod, (method, args) => {
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return stringDecrypter.decrypt((int)args[0]);
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});
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}
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dumpEmbeddedAssemblies();
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}
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void decryptResources() {
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var rsrc = resourceResolver.mergeResources();
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if (rsrc == null)
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return;
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addResourceToBeRemoved(rsrc, "Encrypted resources");
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}
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void dumpEmbeddedAssemblies() {
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foreach (var info in assemblyResolver.AssemblyInfos) {
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dumpEmbeddedFile(info.resource, info.assemblyName, true);
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@ -155,7 +176,16 @@ namespace de4dot.deobfuscators.CryptoObfuscator {
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void dumpEmbeddedFile(EmbeddedResource resource, string assemblyName, bool isAssembly) {
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string extension = isAssembly ? ".dll" : ".pdb";
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DeobfuscatedFile.createAssemblyFile(resourceDecrypter.decrypt(resource.GetResourceStream()), Utils.getAssemblySimpleName(assemblyName), extension);
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addResourceToBeRemoved(resource, string.Format("Embedded assembly{0}: {1}", isAssembly ? "" : " (pdb)", assemblyName));
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string reason = isAssembly ? string.Format("Embedded assembly: {0}", assemblyName) :
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string.Format("Embedded pdb: {0}", assemblyName);
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addResourceToBeRemoved(resource, reason);
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}
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public override IEnumerable<string> getStringDecrypterMethods() {
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var list = new List<string>();
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if (stringDecrypter.StringDecrypterMethod != null)
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list.Add(stringDecrypter.StringDecrypterMethod.MetadataToken.ToInt32().ToString("X8"));
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return list;
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}
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}
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}
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@ -17,6 +17,7 @@
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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 Mono.Cecil;
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using Mono.Cecil.Cil;
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using de4dot.blocks;
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@ -26,6 +27,7 @@ namespace de4dot.deobfuscators.CryptoObfuscator {
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ModuleDefinition module;
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ResourceDecrypter resourceDecrypter;
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TypeDefinition resolverType;
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bool mergedIt = false;
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public ResourceResolver(ModuleDefinition module, ResourceDecrypter resourceDecrypter) {
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this.module = module;
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@ -48,6 +50,19 @@ namespace de4dot.deobfuscators.CryptoObfuscator {
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}
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}
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public EmbeddedResource mergeResources() {
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if (mergedIt)
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return null;
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var resource = DotNetUtils.getResource(module, module.Assembly.Name.Name) as EmbeddedResource;
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if (resource == null)
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throw new ApplicationException("Could not find encrypted resources");
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DeobUtils.decryptAndAddResources(module, resource.Name, () => resourceDecrypter.decrypt(resource.GetResourceStream()));
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mergedIt = true;
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return resource;
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}
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bool checkType(TypeDefinition type, MethodDefinition initMethod) {
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if (!initMethod.HasBody)
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return false;
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120
de4dot.code/deobfuscators/CryptoObfuscator/StringDecrypter.cs
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120
de4dot.code/deobfuscators/CryptoObfuscator/StringDecrypter.cs
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@ -0,0 +1,120 @@
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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.Text;
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using Mono.Cecil;
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using de4dot.blocks;
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namespace de4dot.deobfuscators.CryptoObfuscator {
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class StringDecrypter {
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ModuleDefinition module;
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EmbeddedResource stringResource;
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TypeDefinition stringDecrypterType;
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MethodDefinition stringDecrypterMethod;
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byte[] decryptedData;
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public bool Detected {
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get { return stringDecrypterType != 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 StringDecrypter(ModuleDefinition module) {
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this.module = module;
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}
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public void detect() {
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TypeDefinition type;
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MethodDefinition method;
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if (!findStringDecrypterType(out type, out method))
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return;
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stringDecrypterType = type;
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stringDecrypterMethod = method;
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}
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public void init(ResourceDecrypter resourceDecrypter) {
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if (decryptedData != null)
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return;
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var resourceName = module.Assembly.Name.Name + module.Assembly.Name.Name;
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stringResource = DotNetUtils.getResource(module, resourceName) as EmbeddedResource;
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if (stringResource == null)
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return;
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decryptedData = resourceDecrypter.decrypt(stringResource.GetResourceStream());
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}
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public string decrypt(int index) {
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int len;
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byte b = decryptedData[index++];
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if ((b & 0x80) == 0)
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len = b;
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else if ((b & 0x40) == 0)
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len = ((b & 0x3F) << 8) + decryptedData[index++];
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else {
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len = ((b & 0x3F) << 24) +
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((int)decryptedData[index++] << 16) +
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((int)decryptedData[index++] << 8) +
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decryptedData[index++];
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}
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return Encoding.Unicode.GetString(decryptedData, index, len);
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}
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bool findStringDecrypterType(out TypeDefinition theType, out MethodDefinition theMethod) {
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theType = null;
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theMethod = null;
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foreach (var type in module.Types) {
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if (type.IsPublic)
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continue;
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if (type.Fields.Count != 1)
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continue;
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if (DotNetUtils.findFieldType(type, "System.Byte[]", true) == null)
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continue;
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if (type.Methods.Count != 3)
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continue;
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if (type.HasEvents || type.HasProperties)
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continue;
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MethodDefinition method = null;
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foreach (var m in type.Methods) {
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if (m.Name == ".ctor" || m.Name == ".cctor")
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continue;
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if (DotNetUtils.isMethod(m, "System.String", "(System.Int32)")) {
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method = m;
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continue;
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}
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break;
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}
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if (method == null)
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continue;
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theType = type;
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theMethod = method;
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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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