139 lines
3.5 KiB
C#
139 lines
3.5 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.Text;
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using dnlib.DotNet;
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using de4dot.blocks;
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namespace de4dot.code.deobfuscators.CryptoObfuscator {
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class StringDecrypter {
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ModuleDefMD module;
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EmbeddedResource stringResource;
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TypeDef stringDecrypterType;
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MethodDef 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 TypeDef Type {
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get { return stringDecrypterType; }
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}
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public MethodDef Method {
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get { return stringDecrypterMethod; }
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}
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public EmbeddedResource Resource {
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get { return stringResource; }
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}
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public StringDecrypter(ModuleDefMD module) {
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this.module = module;
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}
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public void Find() {
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TypeDef type;
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MethodDef 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 Initialize(ResourceDecrypter resourceDecrypter) {
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if (decryptedData != null || stringDecrypterType == null)
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return;
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var resourceName = GetResourceName();
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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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Logger.v("Adding string decrypter. Resource: {0}", Utils.ToCsharpString(stringResource.Name));
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decryptedData = resourceDecrypter.Decrypt(stringResource.GetResourceStream());
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}
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string GetResourceName() {
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var defaultName = module.Assembly.Name.String + module.Assembly.Name.String;
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var cctor = stringDecrypterType.FindStaticConstructor();
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if (cctor == null)
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return defaultName;
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foreach (var s in DotNetUtils.GetCodeStrings(cctor)) {
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if (DotNetUtils.GetResource(module, s) != null)
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return s;
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try {
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return Encoding.UTF8.GetString(Convert.FromBase64String(s));
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}
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catch {
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}
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}
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return defaultName;
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}
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public string Decrypt(int index) {
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int len = DeobUtils.ReadVariableLengthInt32(decryptedData, ref index);
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return Encoding.Unicode.GetString(decryptedData, index, len);
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}
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bool FindStringDecrypterType(out TypeDef theType, out MethodDef 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 != 2 && type.Methods.Count != 3)
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continue;
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if (type.NestedTypes.Count > 0)
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continue;
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MethodDef 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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