420 lines
12 KiB
C#
420 lines
12 KiB
C#
/*
|
|
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 <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
using System;
|
|
using System.Collections.Generic;
|
|
using System.IO;
|
|
using System.IO.Compression;
|
|
using System.Security.Cryptography;
|
|
using dnlib.DotNet;
|
|
using dnlib.DotNet.Emit;
|
|
using de4dot.blocks;
|
|
|
|
namespace de4dot.code.deobfuscators.CryptoObfuscator {
|
|
class ResourceDecrypter {
|
|
const int BUFLEN = 0x8000;
|
|
ModuleDefMD module;
|
|
TypeDef resourceDecrypterType;
|
|
byte[] buffer1 = new byte[BUFLEN];
|
|
byte[] buffer2 = new byte[BUFLEN];
|
|
byte desEncryptedFlag;
|
|
byte deflatedFlag;
|
|
byte bitwiseNotEncryptedFlag;
|
|
FrameworkType frameworkType;
|
|
bool flipFlagsBits;
|
|
bool skipBeforeFlag;
|
|
int skipBytes;
|
|
|
|
public ResourceDecrypter(ModuleDefMD module, ISimpleDeobfuscator simpleDeobfuscator) {
|
|
this.module = module;
|
|
frameworkType = DotNetUtils.GetFrameworkType(module);
|
|
Find(simpleDeobfuscator);
|
|
}
|
|
|
|
void Find(ISimpleDeobfuscator simpleDeobfuscator) {
|
|
switch (frameworkType) {
|
|
case FrameworkType.Silverlight:
|
|
FindSilverlight();
|
|
break;
|
|
|
|
case FrameworkType.Desktop:
|
|
case FrameworkType.CompactFramework:
|
|
if (!module.IsClr1x) {
|
|
if (FindDesktopOrCompactFramework())
|
|
break;
|
|
}
|
|
FindDesktopOrCompactFrameworkV1();
|
|
break;
|
|
}
|
|
|
|
InitializeHeaderInfo(simpleDeobfuscator);
|
|
}
|
|
|
|
static string[] requiredTypes = new string[] {
|
|
"System.IO.MemoryStream",
|
|
"System.Object",
|
|
"System.Int32",
|
|
};
|
|
bool FindDesktopOrCompactFramework() {
|
|
resourceDecrypterType = null;
|
|
foreach (var type in module.Types) {
|
|
if (type.Fields.Count < 5)
|
|
continue;
|
|
if (!new FieldTypes(type).All(requiredTypes))
|
|
continue;
|
|
|
|
var cctor = type.FindStaticConstructor();
|
|
if (cctor == null)
|
|
continue;
|
|
|
|
if (!CheckCctor(cctor))
|
|
continue;
|
|
|
|
resourceDecrypterType = type;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
bool CheckCctor(MethodDef cctor) {
|
|
if (cctor.Body == null)
|
|
return false;
|
|
int stsfldCount = 0;
|
|
foreach (var instr in cctor.Body.Instructions) {
|
|
if (instr.OpCode.Code == Code.Stsfld) {
|
|
var field = instr.Operand as IField;
|
|
if (!new SigComparer().Equals(cctor.DeclaringType, field.DeclaringType))
|
|
return false;
|
|
stsfldCount++;
|
|
}
|
|
}
|
|
return stsfldCount >= cctor.DeclaringType.Fields.Count;
|
|
}
|
|
|
|
static string[] requiredLocals_v1 = new string[] {
|
|
"System.Boolean",
|
|
"System.Byte",
|
|
"System.Byte[]",
|
|
"System.Int32",
|
|
"System.Security.Cryptography.DESCryptoServiceProvider",
|
|
};
|
|
bool FindDesktopOrCompactFrameworkV1() {
|
|
resourceDecrypterType = null;
|
|
foreach (var type in module.Types) {
|
|
if (type.Fields.Count != 0)
|
|
continue;
|
|
|
|
foreach (var method in GetDecrypterMethods(type)) {
|
|
if (method == null)
|
|
continue;
|
|
if (!new LocalTypes(method).Exactly(requiredLocals_v1))
|
|
continue;
|
|
if (!DotNetUtils.CallsMethod(method, "System.Int64", "()"))
|
|
continue;
|
|
if (!DotNetUtils.CallsMethod(method, "System.Int32", "(System.Byte[],System.Int32,System.Int32)"))
|
|
continue;
|
|
if (!DotNetUtils.CallsMethod(method, "System.Void", "(System.Array,System.Int32,System.Array,System.Int32,System.Int32)"))
|
|
continue;
|
|
if (!DotNetUtils.CallsMethod(method, "System.Security.Cryptography.ICryptoTransform", "()"))
|
|
continue;
|
|
if (!DotNetUtils.CallsMethod(method, "System.Byte[]", "(System.Byte[],System.Int32,System.Int32)"))
|
|
continue;
|
|
|
|
resourceDecrypterType = type;
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
static string[] requiredLocals_sl = new string[] {
|
|
"System.Byte",
|
|
"System.Byte[]",
|
|
"System.Int32",
|
|
};
|
|
void FindSilverlight() {
|
|
foreach (var type in module.Types) {
|
|
if (type.Fields.Count > 0)
|
|
continue;
|
|
if (type.HasNestedTypes || type.HasGenericParameters)
|
|
continue;
|
|
|
|
foreach (var method in GetDecrypterMethods(type)) {
|
|
if (method == null)
|
|
continue;
|
|
if (!new LocalTypes(method).All(requiredLocals_sl))
|
|
continue;
|
|
|
|
resourceDecrypterType = type;
|
|
return;
|
|
}
|
|
}
|
|
}
|
|
|
|
void InitializeHeaderInfo(ISimpleDeobfuscator simpleDeobfuscator) {
|
|
skipBytes = 0;
|
|
|
|
foreach (var method in GetDecrypterMethods(resourceDecrypterType)) {
|
|
if (UpdateFlags(method, simpleDeobfuscator))
|
|
return;
|
|
}
|
|
|
|
desEncryptedFlag = 1;
|
|
deflatedFlag = 2;
|
|
bitwiseNotEncryptedFlag = 4;
|
|
}
|
|
|
|
static bool CheckFlipBits(MethodDef method, out int index) {
|
|
int nots = 0, i;
|
|
var instrs = method.Body.Instructions;
|
|
index = -1;
|
|
for (i = 0; i < instrs.Count - 1; i++) {
|
|
var ldloc = instrs[i];
|
|
if (!ldloc.IsLdloc())
|
|
continue;
|
|
var local = ldloc.GetLocal(method.Body.Variables);
|
|
if (local == null || local.Type.GetElementType().GetPrimitiveSize() < 0)
|
|
continue;
|
|
if (instrs[i + 1].OpCode.Code == Code.Not) {
|
|
nots++;
|
|
index = i + 1;
|
|
}
|
|
}
|
|
return (nots & 1) == 1;
|
|
}
|
|
|
|
bool UpdateFlags(MethodDef method, ISimpleDeobfuscator simpleDeobfuscator) {
|
|
if (method == null || method.Body == null || method.Body.Variables.Count < 3)
|
|
return false;
|
|
|
|
var constants = new List<int>();
|
|
simpleDeobfuscator.Deobfuscate(method);
|
|
var instructions = method.Body.Instructions;
|
|
for (int i = 2; i < instructions.Count; i++) {
|
|
var and = instructions[i];
|
|
if (and.OpCode.Code != Code.And)
|
|
continue;
|
|
var ldci4 = instructions[i - 1];
|
|
if (!ldci4.IsLdcI4())
|
|
continue;
|
|
int flagValue = ldci4.GetLdcI4Value();
|
|
if (!IsFlag(flagValue))
|
|
continue;
|
|
var ldloc = instructions[i - 2];
|
|
if (!ldloc.IsLdloc())
|
|
continue;
|
|
var local = ldloc.GetLocal(method.Body.Variables);
|
|
if (local.Type.GetElementType().GetPrimitiveSize() < 0)
|
|
continue;
|
|
constants.Add(flagValue);
|
|
}
|
|
|
|
int notIndex, skipIndex;
|
|
flipFlagsBits = CheckFlipBits(method, out notIndex);
|
|
skipBytes = GetHeaderSkipBytes(method, out skipIndex);
|
|
skipBeforeFlag = skipIndex < notIndex;
|
|
|
|
switch (frameworkType) {
|
|
case FrameworkType.Desktop:
|
|
if (!module.IsClr1x) {
|
|
if (constants.Count == 2) {
|
|
desEncryptedFlag = (byte)constants[0];
|
|
deflatedFlag = (byte)constants[1];
|
|
return true;
|
|
}
|
|
}
|
|
if (constants.Count == 1) {
|
|
desEncryptedFlag = (byte)constants[0];
|
|
return true;
|
|
}
|
|
break;
|
|
|
|
case FrameworkType.Silverlight:
|
|
if (constants.Count == 1) {
|
|
bitwiseNotEncryptedFlag = (byte)constants[0];
|
|
return true;
|
|
}
|
|
break;
|
|
|
|
case FrameworkType.CompactFramework:
|
|
if (constants.Count == 1) {
|
|
desEncryptedFlag = (byte)constants[0];
|
|
return true;
|
|
}
|
|
break;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static int GetHeaderSkipBytes(MethodDef method, out int index) {
|
|
var instrs = method.Body.Instructions;
|
|
for (int i = 0; i < instrs.Count - 1; i++) {
|
|
var ldci4 = instrs[i];
|
|
if (!ldci4.IsLdcI4())
|
|
continue;
|
|
int loopCount = ldci4.GetLdcI4Value();
|
|
if (loopCount < 2 || loopCount > 4)
|
|
continue;
|
|
var blt = instrs[i + 1];
|
|
if (blt.OpCode.Code != Code.Blt && blt.OpCode.Code != Code.Blt_S && blt.OpCode.Code != Code.Clt)
|
|
continue;
|
|
index = i;
|
|
return loopCount - 1;
|
|
}
|
|
index = 0;
|
|
return 0;
|
|
}
|
|
|
|
static bool IsFlag(int value) {
|
|
for (uint tmp = (uint)value; tmp != 0; tmp >>= 1) {
|
|
if ((tmp & 1) != 0)
|
|
return tmp == 1;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
static IEnumerable<MethodDef> GetDecrypterMethods(TypeDef type) {
|
|
if (type == null)
|
|
yield break;
|
|
foreach (var method in type.Methods) {
|
|
if (DotNetUtils.IsMethod(method, "System.Byte[]", "(System.IO.Stream)"))
|
|
yield return method;
|
|
else if (DotNetUtils.IsMethod(method, "System.Byte[]", "(System.Int64,System.IO.Stream)"))
|
|
yield return method;
|
|
else if (DotNetUtils.IsMethod(method, "System.Byte[]", "(System.Int64,System.IO.Stream,System.UInt32)"))
|
|
yield return method;
|
|
else if (DotNetUtils.IsMethod(method, "System.Byte[]", "(System.Int32,System.IO.Stream)"))
|
|
yield return method;
|
|
else if (DotNetUtils.IsMethod(method, "System.Byte[]", "(System.Int16,System.IO.Stream)"))
|
|
yield return method;
|
|
else if (DotNetUtils.IsMethod(method, "System.Byte[]", "(System.Byte,System.IO.Stream)"))
|
|
yield return method;
|
|
else if (DotNetUtils.IsMethod(method, "System.Byte[]", "(System.SByte,System.IO.Stream)"))
|
|
yield return method;
|
|
else if (DotNetUtils.IsMethod(method, "System.Byte[]", "(System.Byte,System.IO.Stream,System.Int32)"))
|
|
yield return method;
|
|
else if (DotNetUtils.IsMethod(method, "System.Byte[]", "(System.SByte,System.IO.Stream,System.UInt32)"))
|
|
yield return method;
|
|
else if (DotNetUtils.IsMethod(method, "System.Byte[]", "(System.Char,System.IO.Stream)"))
|
|
yield return method;
|
|
}
|
|
}
|
|
|
|
public byte[] Decrypt(Stream resourceStream) {
|
|
Stream sourceStream = resourceStream;
|
|
int sourceStreamOffset = 1;
|
|
bool didSomething = false;
|
|
|
|
if (skipBeforeFlag) {
|
|
sourceStream.Position += skipBytes;
|
|
sourceStreamOffset += skipBytes;
|
|
}
|
|
byte flags = (byte)sourceStream.ReadByte();
|
|
if (flipFlagsBits)
|
|
flags = (byte)~flags;
|
|
if (!skipBeforeFlag) {
|
|
sourceStream.Position += skipBytes;
|
|
sourceStreamOffset += skipBytes;
|
|
}
|
|
|
|
byte allFlags = (byte)(desEncryptedFlag | deflatedFlag | bitwiseNotEncryptedFlag);
|
|
if ((flags & ~allFlags) != 0)
|
|
Logger.w("Found unknown resource encryption flags: 0x{0:X2}", flags);
|
|
|
|
if ((flags & desEncryptedFlag) != 0) {
|
|
var memStream = new MemoryStream((int)resourceStream.Length);
|
|
using (var provider = new DESCryptoServiceProvider()) {
|
|
var iv = new byte[8];
|
|
sourceStream.Read(iv, 0, 8);
|
|
provider.IV = iv;
|
|
provider.Key = GetKey(sourceStream);
|
|
|
|
using (var transform = provider.CreateDecryptor()) {
|
|
while (true) {
|
|
int count = sourceStream.Read(buffer1, 0, buffer1.Length);
|
|
if (count <= 0)
|
|
break;
|
|
int count2 = transform.TransformBlock(buffer1, 0, count, buffer2, 0);
|
|
memStream.Write(buffer2, 0, count2);
|
|
}
|
|
var finalData = transform.TransformFinalBlock(buffer1, 0, 0);
|
|
memStream.Write(finalData, 0, finalData.Length);
|
|
}
|
|
}
|
|
sourceStream = memStream;
|
|
sourceStreamOffset = 0;
|
|
didSomething = true;
|
|
}
|
|
|
|
if ((flags & deflatedFlag) != 0) {
|
|
var memStream = new MemoryStream((int)resourceStream.Length);
|
|
sourceStream.Position = sourceStreamOffset;
|
|
using (var inflater = new DeflateStream(sourceStream, CompressionMode.Decompress)) {
|
|
while (true) {
|
|
int count = inflater.Read(buffer1, 0, buffer1.Length);
|
|
if (count <= 0)
|
|
break;
|
|
memStream.Write(buffer1, 0, count);
|
|
}
|
|
}
|
|
|
|
sourceStream = memStream;
|
|
sourceStreamOffset = 0;
|
|
didSomething = true;
|
|
}
|
|
|
|
if ((flags & bitwiseNotEncryptedFlag) != 0) {
|
|
var memStream = new MemoryStream((int)resourceStream.Length);
|
|
sourceStream.Position = sourceStreamOffset;
|
|
for (int i = sourceStreamOffset; i < sourceStream.Length; i++)
|
|
memStream.WriteByte((byte)~sourceStream.ReadByte());
|
|
|
|
sourceStream = memStream;
|
|
sourceStreamOffset = 0;
|
|
didSomething = true;
|
|
}
|
|
|
|
if (didSomething && sourceStream is MemoryStream) {
|
|
var memStream = (MemoryStream)sourceStream;
|
|
return memStream.ToArray();
|
|
}
|
|
else {
|
|
int len = (int)(sourceStream.Length - sourceStream.Position);
|
|
byte[] data = new byte[len];
|
|
sourceStream.Read(data, 0, len);
|
|
return data;
|
|
}
|
|
}
|
|
|
|
byte[] GetKey(Stream resourceStream) {
|
|
byte[] key = new byte[8];
|
|
resourceStream.Read(key, 0, key.Length);
|
|
for (int i = 0; i < key.Length; i++) {
|
|
if (key[i] != 0)
|
|
return key;
|
|
}
|
|
key = PublicKeyBase.GetRawData(module.Assembly.PublicKeyToken);
|
|
if (key == null)
|
|
throw new ApplicationException("PublicKeyToken is null, can't decrypt resources");
|
|
return key;
|
|
}
|
|
}
|
|
}
|