/*
Copyright (C) 2011-2014 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.Collections.Generic;
using System.IO;
using dnlib.IO;
using dnlib.DotNet;
using dnlib.DotNet.Emit;
using de4dot.blocks;
namespace de4dot.code.deobfuscators.Babel_NET {
class ResourceResolver {
ModuleDefMD module;
ResourceDecrypter resourceDecrypter;
ISimpleDeobfuscator simpleDeobfuscator;
TypeDef resolverType;
MethodDef registerMethod;
EmbeddedResource encryptedResource;
bool hasXorKeys;
int xorKey1, xorKey2;
public bool Detected {
get { return resolverType != null; }
}
public TypeDef Type {
get { return resolverType; }
}
public MethodDef InitMethod {
get { return registerMethod; }
}
public ResourceResolver(ModuleDefMD module, ResourceDecrypter resourceDecrypter, ISimpleDeobfuscator simpleDeobfuscator) {
this.module = module;
this.resourceDecrypter = resourceDecrypter;
this.simpleDeobfuscator = simpleDeobfuscator;
}
public void Find() {
var requiredTypes = new string[] {
"System.Reflection.Assembly",
"System.Object",
"System.Int32",
"System.String[]",
};
foreach (var type in module.Types) {
if (type.HasEvents)
continue;
if (!new FieldTypes(type).All(requiredTypes))
continue;
MethodDef regMethod, handler;
if (!BabelUtils.FindRegisterMethod(type, out regMethod, out handler))
continue;
var resource = BabelUtils.FindEmbeddedResource(module, type);
if (resource == null)
continue;
var decryptMethod = FindDecryptMethod(type);
if (decryptMethod == null)
throw new ApplicationException("Couldn't find resource type decrypt method");
resourceDecrypter.DecryptMethod = ResourceDecrypter.FindDecrypterMethod(decryptMethod);
InitXorKeys(decryptMethod);
resolverType = type;
registerMethod = regMethod;
encryptedResource = resource;
return;
}
}
static MethodDef FindDecryptMethod(TypeDef type) {
foreach (var method in type.Methods) {
if (!DotNetUtils.IsMethod(method, "System.Reflection.Assembly", "(System.IO.Stream)"))
continue;
return method;
}
return null;
}
void InitXorKeys(MethodDef method) {
simpleDeobfuscator.Deobfuscate(method);
var ints = new List();
var instrs = method.Body.Instructions;
for (int i = 0; i < instrs.Count; i++) {
var callvirt = instrs[i];
if (callvirt.OpCode.Code != Code.Callvirt)
continue;
var calledMethod = callvirt.Operand as IMethod;
if (calledMethod == null)
continue;
if (calledMethod.FullName != "System.Int32 System.IO.BinaryReader::ReadInt32()")
continue;
var ldci4 = instrs[i + 1];
if (!ldci4.IsLdcI4())
continue;
if (instrs[i + 2].OpCode.Code != Code.Xor)
continue;
ints.Add(ldci4.GetLdcI4Value());
}
if (ints.Count == 2) {
hasXorKeys = true;
xorKey1 = ints[0];
xorKey2 = ints[1];
}
}
public EmbeddedResource MergeResources() {
if (encryptedResource == null)
return null;
DeobUtils.DecryptAndAddResources(module, encryptedResource.Name.String, () => DecryptResourceAssembly());
var result = encryptedResource;
encryptedResource = null;
return result;
}
byte[] DecryptResourceAssembly() {
var decrypted = resourceDecrypter.Decrypt(encryptedResource.Data.ReadAllBytes());
var reader = new BinaryReader(new MemoryStream(decrypted));
int numResources = reader.ReadInt32() ^ xorKey1;
for (int i = 0; i < numResources; i++)
reader.ReadString();
int len;
if (hasXorKeys)
len = reader.ReadInt32() ^ xorKey2;
else
len = (int)(reader.BaseStream.Length - reader.BaseStream.Position);
return reader.ReadBytes(len);
}
}
}