/*
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.Collections.Generic;
using System.Text;
using dnlib.IO;
using dnlib.DotNet;
using dnlib.DotNet.Emit;
using de4dot.blocks;
namespace de4dot.code.deobfuscators.CryptoObfuscator {
class ConstantsDecrypter {
ModuleDefMD module;
TypeDef decrypterType;
MethodDef methodI4;
MethodDef methodI8;
MethodDef methodR4;
MethodDef methodR8;
MethodDef methodArray;
InitializedDataCreator initializedDataCreator;
EmbeddedResource encryptedResource;
byte[] constantsData;
public TypeDef Type {
get { return decrypterType; }
}
public EmbeddedResource Resource {
get { return encryptedResource; }
}
public MethodDef Int32Decrypter {
get { return methodI4; }
}
public MethodDef Int64Decrypter {
get { return methodI8; }
}
public MethodDef SingleDecrypter {
get { return methodR4; }
}
public MethodDef DoubleDecrypter {
get { return methodR8; }
}
public bool Detected {
get { return decrypterType != null; }
}
public ConstantsDecrypter(ModuleDefMD module, InitializedDataCreator initializedDataCreator) {
this.module = module;
this.initializedDataCreator = initializedDataCreator;
}
public void Find() {
foreach (var type in module.Types) {
if (!CheckType(type))
continue;
decrypterType = type;
return;
}
}
static readonly string[] requiredTypes = new string[] {
"System.Byte[]",
};
bool CheckType(TypeDef type) {
if (type.Methods.Count != 7)
return false;
if (type.Fields.Count < 1 || type.Fields.Count > 2)
return false;
if (!new FieldTypes(type).All(requiredTypes))
return false;
if (!CheckMethods(type))
return false;
return true;
}
bool CheckMethods(TypeDef type) {
methodI4 = DotNetUtils.GetMethod(type, "System.Int32", "(System.Int32)");
methodI8 = DotNetUtils.GetMethod(type, "System.Int64", "(System.Int32)");
methodR4 = DotNetUtils.GetMethod(type, "System.Single", "(System.Int32)");
methodR8 = DotNetUtils.GetMethod(type, "System.Double", "(System.Int32)");
methodArray = DotNetUtils.GetMethod(type, "System.Void", "(System.Array,System.Int32)");
return methodI4 != null && methodI8 != null &&
methodR4 != null && methodR8 != null &&
methodArray != null;
}
public void Initialize(ResourceDecrypter resourceDecrypter) {
if (decrypterType == null)
return;
encryptedResource = CoUtils.GetResource(module, DotNetUtils.GetCodeStrings(decrypterType.FindStaticConstructor()));
encryptedResource.Data.Position = 0;
constantsData = resourceDecrypter.Decrypt(encryptedResource.Data.CreateStream());
}
public int DecryptInt32(int index) {
return BitConverter.ToInt32(constantsData, index);
}
public long DecryptInt64(int index) {
return BitConverter.ToInt64(constantsData, index);
}
public float DecryptSingle(int index) {
return BitConverter.ToSingle(constantsData, index);
}
public double DecryptDouble(int index) {
return BitConverter.ToDouble(constantsData, index);
}
struct ArrayInfo {
public CorLibTypeSig arrayType;
public int start, len;
public int arySize, index;
public ArrayInfo(int start, int len, CorLibTypeSig arrayType, int arySize, int index) {
this.start = start;
this.len = len;
this.arrayType = arrayType;
this.arySize = arySize;
this.index = index;
}
}
public void Deobfuscate(Blocks blocks) {
var infos = new List();
foreach (var block in blocks.MethodBlocks.GetAllBlocks()) {
var instrs = block.Instructions;
infos.Clear();
for (int i = 0; i < instrs.Count - 5; i++) {
int index = i;
var ldci4_arySize = instrs[index++];
if (!ldci4_arySize.IsLdcI4())
continue;
var newarr = instrs[index++];
if (newarr.OpCode.Code != Code.Newarr)
continue;
var arrayType = module.CorLibTypes.GetCorLibTypeSig(newarr.Operand as ITypeDefOrRef);
if (arrayType == null)
continue;
if (instrs[index++].OpCode.Code != Code.Dup)
continue;
var ldci4_index = instrs[index++];
if (!ldci4_index.IsLdcI4())
continue;
var call = instrs[index++];
if (call.OpCode.Code != Code.Call && call.OpCode.Code != Code.Callvirt)
continue;
if (!MethodEqualityComparer.CompareDeclaringTypes.Equals(call.Operand as IMethod, methodArray))
continue;
if (arrayType.ElementType.GetPrimitiveSize() == -1) {
Logger.w("Can't decrypt non-primitive type array in method {0:X8}", blocks.Method.MDToken.ToInt32());
continue;
}
infos.Add(new ArrayInfo(i, index - i, arrayType, ldci4_arySize.GetLdcI4Value(),
ldci4_index.GetLdcI4Value()));
}
infos.Reverse();
foreach (var info in infos) {
var elemSize = info.arrayType.ElementType.GetPrimitiveSize();
var decrypted = DecryptArray(info);
initializedDataCreator.AddInitializeArrayCode(block, info.start, info.len, info.arrayType.ToTypeDefOrRef(), decrypted);
Logger.v("Decrypted {0} array: {1} elements", info.arrayType.ToString(), decrypted.Length / elemSize);
}
}
}
byte[] DecryptArray(ArrayInfo aryInfo) {
var ary = new byte[aryInfo.arySize * aryInfo.arrayType.ElementType.GetPrimitiveSize()];
int dataIndex = aryInfo.index;
int len = DeobUtils.ReadVariableLengthInt32(constantsData, ref dataIndex);
Buffer.BlockCopy(constantsData, dataIndex, ary, 0, len);
return ary;
}
}
}