/*
Copyright (C) 2011-2015 de4dot@gmail.com
This file is part of de4dot.
de4dot is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
de4dot is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with de4dot. If not, see .
*/
using System;
using System.Text;
using dnlib.DotNet;
using dnlib.DotNet.Emit;
using de4dot.blocks;
namespace de4dot.code.deobfuscators.Goliath_NET {
class StringDecrypter : DecrypterBase {
IType delegateReturnType;
FieldDef stringStructField;
public TypeDef StringStruct {
get { return Detected && stringStructField != null ? stringStructField.DeclaringType : null; }
}
public StringDecrypter(ModuleDefMD module)
: base(module) {
}
static string[] requiredFields = new string[] {
"System.Byte[]",
"System.Collections.Generic.Dictionary`2",
};
protected override bool CheckDecrypterType(TypeDef type) {
var fields = type.Fields;
if (fields.Count != 2)
return false;
if (fields[0].FieldType.FullName != "System.Byte[]")
return false;
var dict = fields[1].FieldType.ToGenericInstSig();
if (dict == null || dict.GenericArguments.Count != 2)
return false;
if (dict.GenericType.GetFullName() != "System.Collections.Generic.Dictionary`2")
return false;
if (dict.GenericArguments[0].FullName != "System.Int32")
return false;
var garg = dict.GenericArguments[1];
if (garg.FullName != "System.String") {
if (!garg.IsValueType)
return false;
var gargType = DotNetUtils.GetType(module, garg);
if (gargType == null || !gargType.IsClass)
return false;
if (gargType.Fields.Count != 1)
return false;
var field = gargType.Fields[0];
if (field.FieldType.FullName != "System.String")
return false;
delegateReturnType = gargType;
stringStructField = field;
}
else {
delegateReturnType = garg;
stringStructField = null;
}
return true;
}
protected override bool CheckDelegateInvokeMethod(MethodDef invokeMethod) {
return DotNetUtils.IsMethod(invokeMethod, delegateReturnType.FullName, "(System.Int32)");
}
public string Decrypt(MethodDef method) {
var info = GetInfo(method);
decryptedReader.BaseStream.Position = info.offset;
int len = decryptedReader.ReadInt32();
return Encoding.UTF8.GetString(decryptedReader.ReadBytes(len));
}
public void Deobfuscate(Blocks blocks) {
if (!Detected)
return;
if (stringStructField == null)
return;
foreach (var block in blocks.MethodBlocks.GetAllBlocks()) {
var instrs = block.Instructions;
for (int i = 0; i < instrs.Count - 1; i++) {
var ldstr = instrs[i];
if (ldstr.OpCode.Code != Code.Ldstr)
continue;
var ldfld = instrs[i + 1];
if (ldfld.OpCode.Code != Code.Ldfld)
continue;
if (!FieldEqualityComparer.CompareDeclaringTypes.Equals(stringStructField, ldfld.Operand as IField))
continue;
block.Remove(i + 1, 1);
}
}
}
}
}