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v4.0.0
de4dot-cex/de4dot.code/deobfuscators/ConfuserEx/ResourceDecrypter.cs
ViR Dash 7adf818194 Implement ConfuserEx generic constants and resource decryption; misc improvements 
Move BeaEngine.dll to /bin/
Make sure BeaEngine.dll is loaded when the working directory is different
Disable file deobfuscation exception handler
Don't remove LZMA methods by default
Trim version read from ConfuserAttribute
Minor refactoring
2017-08-20 16:25:25 +03:00

281 lines
11 KiB
C#
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using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using de4dot.blocks;
using dnlib.DotNet;
using dnlib.DotNet.Emit;
using dnlib.DotNet.Writer;
using FieldAttributes = dnlib.DotNet.FieldAttributes;
using MethodAttributes = dnlib.DotNet.MethodAttributes;
using TypeAttributes = dnlib.DotNet.TypeAttributes;
namespace de4dot.code.deobfuscators.ConfuserEx
{
public class ResourceDecrypter
{
private FieldDef _arrayField, _asmField;
private byte[] _decryptedBytes;
private readonly ISimpleDeobfuscator _deobfuscator;
private readonly MethodDef _lzmaMethod;
private readonly ModuleDef _module;
public ResourceDecrypter(ModuleDef module, MethodDef lzmaMethod, ISimpleDeobfuscator deobfsucator)
{
this._module = module;
this._lzmaMethod = lzmaMethod;
_deobfuscator = deobfsucator;
}
public bool CanRemoveLzma { get; private set; }
public TypeDef Type { get; private set; }
public MethodDef Method { get; private set; }
public MethodDef AssembyResolveMethod { get; private set; }
public List<FieldDef> Fields => new List<FieldDef> {_arrayField, _asmField};
public bool Detected => Method != null && _decryptedBytes != null && _arrayField != null && _asmField != null;
public void Find()
{
var moduleCctor = DotNetUtils.GetModuleTypeCctor(_module);
if (moduleCctor == null)
return;
foreach (var inst in moduleCctor.Body.Instructions)
{
if (inst.OpCode != OpCodes.Call)
continue;
if (!(inst.Operand is MethodDef))
continue;
var method = inst.Operand as MethodDef;
if (!method.HasBody || !method.IsStatic)
continue;
if (!DotNetUtils.IsMethod(method, "System.Void", "()"))
continue;
_deobfuscator.Deobfuscate(method, SimpleDeobfuscatorFlags.Force);
if (!IsResDecryptInit(method, out FieldDef aField, out FieldDef asmField, out MethodDef mtd))
continue;
try
{
_decryptedBytes = DecryptArray(method, aField.InitialValue);
}
catch(Exception e)
{
Console.WriteLine(e.Message);
return;
}
_arrayField = aField;
Type = DotNetUtils.GetType(_module, aField.FieldSig.Type);
_asmField = asmField;
AssembyResolveMethod = mtd;
Method = method;
CanRemoveLzma = true;
}
}
private bool IsResDecryptInit(MethodDef method, out FieldDef aField, out FieldDef asField, out MethodDef mtd)
{
aField = null;
asField = null;
mtd = null;
var instr = method.Body.Instructions;
if (instr.Count < 15)
return false;
if (!instr[0].IsLdcI4())
return false;
if (!instr[1].IsStloc()) //uint num = 96u;
return false;
if (!instr[2].IsLdcI4())
return false;
if (instr[0].GetLdcI4Value() != instr[2].GetLdcI4Value())
return false;
if (instr[3].OpCode != OpCodes.Newarr)
return false;
if (instr[3].Operand.ToString() != "System.UInt32")
return false;
if (instr[4].OpCode != OpCodes.Dup)
return false;
if (instr[5].OpCode != OpCodes.Ldtoken)
return false;
aField = instr[5].Operand as FieldDef;
if (aField?.InitialValue == null)
return false;
if (aField.Attributes != (FieldAttributes.Assembly | FieldAttributes.Static | FieldAttributes.HasFieldRVA))
return false;
if (instr[6].OpCode != OpCodes.Call)
return false;
if (instr[6].Operand.ToString() !=
"System.Void System.Runtime.CompilerServices.RuntimeHelpers::InitializeArray(System.Array,System.RuntimeFieldHandle)"
)
return false;
if (!instr[7].IsStloc()) // uint[] array = new uint[] {.....};
return false;
var l = instr.Count;
if (!instr[l - 10].IsLdloc())
return false;
if (instr[l - 9].OpCode != OpCodes.Call)
return false;
if (instr[l - 9].Operand != _lzmaMethod)
return false;
if (instr[l - 8].OpCode != OpCodes.Call)
return false;
if (instr[l - 8].Operand.ToString() !=
"System.Reflection.Assembly System.Reflection.Assembly::Load(System.Byte[])")
return false;
if (instr[l - 7].OpCode != OpCodes.Stsfld) //<Module>.assembly_0 = Assembly.Load(array4);
return false;
asField = instr[l - 7].Operand as FieldDef;
if (asField == null)
return false;
if (instr[l - 6].OpCode != OpCodes.Call)
return false;
if (instr[l - 6].Operand.ToString() != "System.AppDomain System.AppDomain::get_CurrentDomain()")
return false;
if (instr[l - 5].OpCode != OpCodes.Ldnull)
return false;
if (instr[l - 4].OpCode != OpCodes.Ldftn)
return false;
mtd = instr[l - 4].Operand as MethodDef;
if (mtd == null)
return false;
if (DotNetUtils.IsMethod(mtd, "", "()"))
return false;
_deobfuscator.Deobfuscate(mtd, SimpleDeobfuscatorFlags.Force);
if (!IsAssembyResolveMethod(mtd, asField))
return false;
if (instr[l - 3].OpCode != OpCodes.Newobj)
return false;
if (instr[l - 2].OpCode != OpCodes.Callvirt)
//AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(<Module>.smethod_1);
return false;
return true;
}
private byte[] DecryptArray(MethodDef method, byte[] encryptedArray)
{
ModuleDefUser tempModule = new ModuleDefUser("TempModule");
AssemblyDef tempAssembly = new AssemblyDefUser("TempAssembly");
tempAssembly.Modules.Add(tempModule);
var tempType = new TypeDefUser("", "TempType", tempModule.CorLibTypes.Object.TypeDefOrRef);
tempType.Attributes = TypeAttributes.Public | TypeAttributes.Class;
MethodDef tempMethod = Utils.Clone(method);
tempMethod.ReturnType = new SZArraySig(tempModule.CorLibTypes.Byte);
tempMethod.MethodSig.Params.Add(new SZArraySig(tempModule.CorLibTypes.Byte));
tempMethod.Attributes = MethodAttributes.Public | MethodAttributes.Static;
for (int i = 0; i < 5; i++)
tempMethod.Body.Instructions.RemoveAt(2); // read encrypted array from argument
tempMethod.Body.Instructions.Insert(2, OpCodes.Ldarg_0.ToInstruction());
for (int i = 0; i < 8; i++)
tempMethod.Body.Instructions.RemoveAt(tempMethod.Body.Instructions.Count -
2); // make return decrypted array
tempType.Methods.Add(tempMethod);
tempModule.Types.Add(tempType);
using (MemoryStream memoryStream = new MemoryStream())
{
ModuleWriterOptions moduleWriterOptions = new ModuleWriterOptions();
moduleWriterOptions.MetaDataOptions = new MetaDataOptions();
tempModule.Write(memoryStream, moduleWriterOptions);
Assembly patchedAssembly = Assembly.Load(memoryStream.ToArray());
var type = patchedAssembly.ManifestModule.GetType("TempType");
var methods = type.GetMethods();
MethodInfo patchedMethod = methods.First(m => m.IsPublic && m.IsStatic);
byte[] decryptedBytes = (byte[]) patchedMethod.Invoke(null, new object[]{encryptedArray});
return Lzma.Decompress(decryptedBytes);
}
}
private bool IsAssembyResolveMethod(MethodDef method, FieldDef field)
{
var instr = method.Body.Instructions;
if (instr.Count != 10)
return false;
if (instr[0].OpCode != OpCodes.Ldsfld)
return false;
if (instr[0].Operand != field)
return false;
if (instr[1].OpCode != OpCodes.Callvirt)
return false;
if (instr[1].Operand.ToString() != "System.String System.Reflection.Assembly::get_FullName()")
return false;
if (!instr[2].IsLdarg())
return false;
if (instr[3].OpCode != OpCodes.Callvirt)
return false;
if (instr[3].Operand.ToString() != "System.String System.ResolveEventArgs::get_Name()")
return false;
if (instr[4].OpCode != OpCodes.Call)
return false;
if (instr[4].Operand.ToString() != "System.Boolean System.String::op_Equality(System.String,System.String)")
return false;
if (!instr[5].IsBrfalse())
return false;
if (instr[6].OpCode != OpCodes.Ldsfld)
return false;
if (instr[6].Operand != field)
return false;
if (instr[7].OpCode != OpCodes.Ret)
return false;
if (instr[8].OpCode != OpCodes.Ldnull)
return false;
if (instr[9].OpCode != OpCodes.Ret)
return false;
return true;
}
public void Fix()
{
ModuleDef newModule;
try
{
newModule = ModuleDefMD.Load(_decryptedBytes);
}
catch
{
CanRemoveLzma = false;
return;
}
var toRemove = new List<Resource>();
var toAdd = new List<Resource>();
foreach (var cryptedResource in _module.Resources)
foreach (var resource in newModule.Resources)
if (cryptedResource.Name == resource.Name)
{
toRemove.Add(cryptedResource);
toAdd.Add(resource);
}
foreach (var resToRemove in toRemove)
_module.Resources.Remove(resToRemove);
foreach (var resToAdd in toAdd)
_module.Resources.Add(resToAdd);
}
}
}
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