Decrypt CF encrypted strings
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@ -95,6 +95,7 @@
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<Compile Include="deobfuscators\CodeFort\CfMethodCallInliner.cs" />
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<Compile Include="deobfuscators\CodeFort\Deobfuscator.cs" />
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<Compile Include="deobfuscators\CodeFort\ProxyCallFixer.cs" />
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<Compile Include="deobfuscators\CodeFort\StringDecrypter.cs" />
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<Compile Include="deobfuscators\CodeVeil\AssemblyResolver.cs" />
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<Compile Include="deobfuscators\CodeVeil\ErexResourceReader.cs" />
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<Compile Include="deobfuscators\CodeVeil\InvalidDataException.cs" />
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@ -57,6 +57,7 @@ namespace de4dot.code.deobfuscators.CodeFort {
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class Deobfuscator : DeobfuscatorBase {
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Options options;
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ProxyCallFixer proxyCallFixer;
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StringDecrypter stringDecrypter;
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internal class Options : OptionsBase {
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}
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@ -81,7 +82,8 @@ namespace de4dot.code.deobfuscators.CodeFort {
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protected override int detectInternal() {
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int val = 0;
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int sum = toInt32(proxyCallFixer.Detected);
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int sum = toInt32(proxyCallFixer.Detected) +
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toInt32(stringDecrypter.Detected);
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if (sum > 0)
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val += 100 + 10 * (sum - 1);
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@ -91,11 +93,16 @@ namespace de4dot.code.deobfuscators.CodeFort {
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protected override void scanForObfuscator() {
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proxyCallFixer = new ProxyCallFixer(module);
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proxyCallFixer.findDelegateCreator();
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stringDecrypter = new StringDecrypter(module);
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stringDecrypter.find();
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}
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public override void deobfuscateBegin() {
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base.deobfuscateBegin();
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staticStringInliner.add(stringDecrypter.Method, (method, args) => stringDecrypter.decrypt((string)args[0]));
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DeobfuscatedFile.stringDecryptersAdded();
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proxyCallFixer.find();
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}
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@ -113,11 +120,15 @@ namespace de4dot.code.deobfuscators.CodeFort {
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public override void deobfuscateEnd() {
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removeProxyDelegates(proxyCallFixer);
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if (CanRemoveStringDecrypterType)
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addTypeToBeRemoved(stringDecrypter.Type, "String decrypter type");
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base.deobfuscateEnd();
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}
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public override IEnumerable<int> getStringDecrypterMethods() {
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var list = new List<int>();
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if (stringDecrypter.Method != null)
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list.Add(stringDecrypter.Method.MetadataToken.ToInt32());
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return list;
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}
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}
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98
de4dot.code/deobfuscators/CodeFort/StringDecrypter.cs
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98
de4dot.code/deobfuscators/CodeFort/StringDecrypter.cs
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@ -0,0 +1,98 @@
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/*
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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.Text;
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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.CodeFort {
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class StringDecrypter {
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ModuleDefinition module;
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MethodDefinition decryptMethod;
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public bool Detected {
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get { return decryptMethod != null; }
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}
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public MethodDefinition Method {
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get { return decryptMethod; }
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}
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public TypeDefinition Type {
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get { return decryptMethod == null ? null : decryptMethod.DeclaringType; }
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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 find() {
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foreach (var type in module.Types) {
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var method = checkType(type);
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if (method == null)
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continue;
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decryptMethod = method;
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}
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}
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static MethodDefinition checkType(TypeDefinition type) {
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if (type.HasFields)
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return null;
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return checkMethods(type);
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}
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static MethodDefinition checkMethods(TypeDefinition type) {
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MethodDefinition decryptMethod = null;
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foreach (var method in type.Methods) {
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if (method.Name == ".cctor")
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continue;
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if (!method.IsStatic || method.Body == null)
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return null;
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if (!DotNetUtils.isMethod(method, "System.String", "(System.String)"))
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return null;
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if (!hasDouble(method, 3992.0))
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return null;
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decryptMethod = method;
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}
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return decryptMethod;
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}
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static bool hasDouble(MethodDefinition method, double value) {
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if (method == null || method.Body == null)
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return false;
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foreach (var instr in method.Body.Instructions) {
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if (instr.OpCode.Code != Code.Ldc_R8)
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continue;
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if ((double)instr.Operand == value)
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return true;
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}
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return false;
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}
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public string decrypt(string s) {
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var bytes = new byte[s.Length];
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for (int i = 0; i < s.Length; i++)
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bytes[i] = (byte)(s[i] ^ 0x3F);
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return Encoding.UTF8.GetString(bytes);
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}
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}
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}
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