/*
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 System.Security.Cryptography;
using dnlib.PE;
using dnlib.DotNet;
using dnlib.DotNet.Emit;
using de4dot.blocks;
namespace de4dot.code.deobfuscators.Confuser {
abstract class MethodsDecrypterBase : IVersionProvider {
protected ModuleDefMD module;
protected ISimpleDeobfuscator simpleDeobfuscator;
protected MethodDef initMethod;
protected MethodDef decryptMethod;
protected ulong lkey0;
protected uint key0, key1, key2, key3, key4, key5, key6;
protected byte[] methodsData;
public MethodDef InitMethod {
get { return initMethod; }
}
public TypeDef Type {
get { return initMethod != null ? initMethod.DeclaringType : null; }
}
public bool Detected {
get { return initMethod != null; }
}
protected MethodsDecrypterBase(ModuleDefMD module, ISimpleDeobfuscator simpleDeobfuscator) {
this.module = module;
this.simpleDeobfuscator = simpleDeobfuscator;
}
protected MethodsDecrypterBase(ModuleDefMD module, ISimpleDeobfuscator simpleDeobfuscator, MethodsDecrypterBase other) {
this.module = module;
this.simpleDeobfuscator = simpleDeobfuscator;
if (other != null)
this.initMethod = Lookup(other.initMethod, "Could not find initMethod");
}
T Lookup(T def, string errorMessage) where T : class, ICodedToken {
return DeobUtils.Lookup(module, def, errorMessage);
}
public abstract bool GetRevisionRange(out int minRev, out int maxRev);
public void Find() {
Find(DotNetUtils.GetModuleTypeCctor(module));
}
bool Find(MethodDef method) {
if (method == null || method.Body == null)
return false;
foreach (var instr in method.Body.Instructions) {
if (instr.OpCode.Code != Code.Call)
continue;
var calledMethod = instr.Operand as MethodDef;
try {
// If the body is encrypted, this could throw
if (calledMethod == null || calledMethod.Body == null)
continue;
}
catch {
continue;
}
if (!DotNetUtils.IsMethod(calledMethod, "System.Void", "()"))
continue;
if (!CheckType(calledMethod.DeclaringType, calledMethod))
continue;
initMethod = calledMethod;
return true;
}
return false;
}
protected abstract bool CheckType(TypeDef type, MethodDef initMethod);
protected static MethodDef FindDecryptMethod(TypeDef type) {
foreach (var method in type.Methods) {
if (!method.IsStatic || method.Body == null)
continue;
if (!DotNetUtils.IsMethod(method, "System.Byte[]", "(System.Byte[],System.Byte[],System.Byte[])"))
continue;
return method;
}
return null;
}
protected static bool FindLKey0(MethodDef method, out ulong key) {
var instrs = method.Body.Instructions;
for (int index = 0; index < instrs.Count; index++) {
index = FindCallvirtReadUInt64(instrs, index);
if (index < 0)
break;
if (index + 1 >= instrs.Count)
continue;
var ldci8 = instrs[index + 1];
if (ldci8.OpCode.Code != Code.Ldc_I8)
continue;
key = (ulong)(long)ldci8.Operand;
return true;
}
key = 0;
return false;
}
protected static bool FindKey0_v16_r71742(MethodDef method, out uint key) {
var instrs = method.Body.Instructions;
for (int i = 0; i + 5 < instrs.Count; i++) {
i = FindCallvirtReadUInt32(instrs, i);
if (i < 0)
break;
int index = i + 1;
var ldci4_1 = instrs[index++];
if (!ldci4_1.IsLdcI4())
continue;
if (instrs[index++].OpCode.Code != Code.Xor)
continue;
if (!instrs[index++].IsStloc())
continue;
if (!instrs[index++].IsLdloc())
continue;
var ldci4_2 = instrs[index++];
if (!ldci4_2.IsLdcI4())
continue;
if (ldci4_1.GetLdcI4Value() != ldci4_2.GetLdcI4Value())
continue;
key = (uint)ldci4_1.GetLdcI4Value();
return true;
}
key = 0;
return false;
}
protected static bool FindKey0_v14_r58564(MethodDef method, out uint key) {
var instrs = method.Body.Instructions;
for (int i = 0; i + 5 < instrs.Count; i++) {
i = ConfuserUtils.FindCallMethod(instrs, i, Code.Callvirt, "System.Int32 System.IO.BinaryReader::ReadInt32()");
if (i < 0)
break;
int index = i + 1;
var ldci4_1 = instrs[index++];
if (!ldci4_1.IsLdcI4())
continue;
if (instrs[index++].OpCode.Code != Code.Xor)
continue;
if (!instrs[index++].IsStloc())
continue;
if (!instrs[index++].IsLdloc())
continue;
var ldci4_2 = instrs[index++];
if (!ldci4_2.IsLdcI4())
continue;
if (ldci4_2.GetLdcI4Value() != 0 && ldci4_1.GetLdcI4Value() != ldci4_2.GetLdcI4Value())
continue;
key = (uint)ldci4_1.GetLdcI4Value();
return true;
}
key = 0;
return false;
}
protected static bool FindKey1(MethodDef method, out uint key) {
var instrs = method.Body.Instructions;
for (int index = 0; index < instrs.Count; index++) {
index = FindCallvirtReadUInt32(instrs, index);
if (index < 0)
break;
if (index == 0)
continue;
int i = index - 1;
if (!CheckCallvirtReadUInt32(instrs, ref i))
continue;
if (!CheckCallvirtReadUInt32(instrs, ref i))
continue;
if (!CheckCallvirtReadUInt32(instrs, ref i))
continue;
if (!CheckCallvirtReadUInt32(instrs, ref i))
continue;
if (i + 1 >= instrs.Count)
continue;
if (!instrs[i].IsLdloc())
continue;
var ldci4 = instrs[i + 1];
if (!ldci4.IsLdcI4())
continue;
key = (uint)ldci4.GetLdcI4Value();
return true;
}
key = 0;
return false;
}
static bool CheckCallvirtReadUInt32(IList instrs, ref int index) {
if (index + 2 >= instrs.Count)
return false;
if (!instrs[index].IsLdloc())
return false;
if (!ConfuserUtils.IsCallMethod(instrs[index + 1], Code.Callvirt, "System.UInt32 System.IO.BinaryReader::ReadUInt32()"))
return false;
if (!instrs[index + 2].IsStloc() && instrs[index + 2].OpCode.Code != Code.Pop)
return false;
index += 3;
return true;
}
protected static bool FindKey2Key3(MethodDef method, out uint key2, out uint key3) {
var instrs = method.Body.Instructions;
for (int i = 0; i < instrs.Count; i++) {
int index = i;
if (!FindKey2OrKey3(instrs, ref index, out key2))
continue;
if (!FindKey2OrKey3(instrs, ref index, out key3))
continue;
return true;
}
key2 = 0;
key3 = 0;
return false;
}
static bool FindKey2OrKey3(IList instrs, ref int index, out uint key) {
key = 0;
if (index + 6 >= instrs.Count)
return false;
int i = index;
if (!instrs[i++].IsLdloc())
return false;
if (!instrs[i++].IsLdloc())
return false;
if (!ConfuserUtils.IsCallMethod(instrs[i++], Code.Callvirt, "System.Int32 System.IO.BinaryReader::ReadInt32()"))
return false;
var ldci4 = instrs[i++];
if (!ldci4.IsLdcI4())
return false;
if (instrs[i++].OpCode.Code != Code.Xor)
return false;
if (!ConfuserUtils.IsCallMethod(instrs[i++], Code.Callvirt, "System.Byte[] System.IO.BinaryReader::ReadBytes(System.Int32)"))
return false;
if (!instrs[i++].IsStloc())
return false;
key = (uint)ldci4.GetLdcI4Value();
index = i;
return true;
}
protected static bool FindKey6(MethodDef method, out uint key) {
var instrs = method.Body.Instructions;
for (int i = 0; i + 4 < instrs.Count; i++) {
int index = i;
if (!instrs[index++].IsLdloc())
continue;
if (instrs[index++].OpCode.Code != Code.Sub)
continue;
if (instrs[index++].OpCode.Code != Code.Ldelem_U1)
continue;
var ldci4 = instrs[index++];
if (!ldci4.IsLdcI4())
continue;
if (instrs[index++].OpCode.Code != Code.Xor)
continue;
if (instrs[index++].OpCode.Code != Code.Conv_U1)
continue;
key = (uint)ldci4.GetLdcI4Value();
return true;
}
key = 0;
return false;
}
protected static int FindCallvirtReadUInt32(IList instrs, int index) {
return ConfuserUtils.FindCallMethod(instrs, index, Code.Callvirt, "System.UInt32 System.IO.BinaryReader::ReadUInt32()");
}
static int FindCallvirtReadUInt64(IList instrs, int index) {
return ConfuserUtils.FindCallMethod(instrs, index, Code.Callvirt, "System.UInt64 System.IO.BinaryReader::ReadUInt64()");
}
protected byte[] DecryptMethodsData_v17_r73404(MyPEImage peImage) {
return DecryptMethodsData_v16_r71742(peImage, GetEncryptedHeaderOffset_vXX(peImage.Sections));
}
protected byte[] DecryptMethodsData_v16_r71742(MyPEImage peImage, uint encryptedHeaderOffset) {
uint mdRva = peImage.OptionalHeader.CheckSum ^ (uint)key0;
if ((RVA)mdRva != peImage.Cor20Header.MetaData.VirtualAddress)
throw new ApplicationException("Invalid metadata rva");
var reader = peImage.Reader;
reader.Position = encryptedHeaderOffset;
ulong checkSum = reader.ReadUInt64() ^ lkey0;
reader.ReadInt32(); // strong name RVA
reader.ReadInt32(); // strong name len
var iv = reader.ReadBytes(reader.ReadInt32() ^ (int)key2);
var encrypted = reader.ReadBytes(reader.ReadInt32() ^ (int)key3);
var streamsBuffer = GetStreamsBuffer(peImage);
if (checkSum != CalcChecksum(streamsBuffer))
throw new ApplicationException("Invalid checksum. File has been modified.");
var decrypted = Decrypt(encrypted, iv, streamsBuffer);
if (BitConverter.ToInt16(decrypted, 0) != 0x6FD6)
throw new ApplicationException("Invalid magic");
return decrypted;
}
protected uint GetEncryptedHeaderOffset_v16_r71742(IList sections) {
for (int i = sections.Count - 1; i >= 0; i--) {
var section = sections[i];
if (section.DisplayName == ".confuse")
return section.PointerToRawData;
}
throw new ApplicationException("Could not find encrypted section");
}
uint GetEncryptedHeaderOffset_vXX(IList sections) {
for (int i = sections.Count - 1; i >= 0; i--) {
var section = sections[i];
if (GetSectionNameHash(section) == (uint)key1)
return section.PointerToRawData;
}
throw new ApplicationException("Could not find encrypted section");
}
static byte[] GetStreamsBuffer(MyPEImage peImage) {
var memStream = new MemoryStream();
var writer = new BinaryWriter(memStream);
var reader = peImage.Reader;
foreach (var mdStream in peImage.MetaData.AllStreams) {
reader.Position = (long)mdStream.StartOffset;
writer.Write(reader.ReadBytes((int)(mdStream.EndOffset - mdStream.StartOffset)));
}
return memStream.ToArray();
}
protected static ulong CalcChecksum(byte[] data) {
var sum = DeobUtils.Md5Sum(data);
return BitConverter.ToUInt64(sum, 0) ^ BitConverter.ToUInt64(sum, 8);
}
static uint GetSectionNameHash(ImageSectionHeader section) {
uint hash = 0;
foreach (var c in section.Name)
hash += c;
return hash;
}
protected byte[] Decrypt(byte[] encrypted, byte[] iv, byte[] streamsBuffer) {
var decrypted = DeobUtils.AesDecrypt(encrypted, DeobUtils.Sha256Sum(streamsBuffer), iv);
var sha = SHA512.Create();
var hash = sha.ComputeHash(streamsBuffer);
for (int i = 0; i < decrypted.Length; i += 64) {
int j;
for (j = 0; j < 64 && i + j < decrypted.Length; j++)
decrypted[i + j] ^= (byte)(hash[j] ^ key6);
hash = sha.ComputeHash(decrypted, i, j);
}
return decrypted;
}
}
}