/*
Copyright (C) 2011-2012 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.Collections.Generic;
using System.IO;
using System.Text;
using Mono.Cecil;
using Mono.Cecil.Cil;
using de4dot.blocks;
namespace de4dot.code.deobfuscators.Eazfuscator_NET {
class StringDecrypter {
ModuleDefinition module;
TypeDefinition stringType;
MethodDefinition stringMethod;
TypeDefinition dataDecrypterType;
short s1, s2, s3;
int i1, i2, i3, i4, i5;
bool checkMinus2;
bool usePublicKeyToken;
int keyLen;
byte[] theKey;
int magic1;
EmbeddedResource encryptedResource;
BinaryReader reader;
DecrypterType decrypterType;
StreamHelperType streamHelperType;
class StreamHelperType {
public TypeDefinition type;
public MethodDefinition readInt16Method;
public MethodDefinition readInt32Method;
public MethodDefinition readBytesMethod;
public bool Detected {
get {
return readInt16Method != null &&
readInt32Method != null &&
readBytesMethod != null;
}
}
public StreamHelperType(TypeDefinition type) {
this.type = type;
foreach (var method in type.Methods) {
if (method.IsStatic || method.Body == null || method.IsPrivate || method.GenericParameters.Count > 0)
continue;
if (DotNetUtils.isMethod(method, "System.Int16", "()"))
readInt16Method = method;
else if (DotNetUtils.isMethod(method, "System.Int32", "()"))
readInt32Method = method;
else if (DotNetUtils.isMethod(method, "System.Byte[]", "(System.Int32)"))
readBytesMethod = method;
}
}
}
public TypeDefinition Type {
get { return stringType; }
}
public EmbeddedResource Resource {
get { return encryptedResource; }
}
public IEnumerable Types {
get {
return new List {
stringType,
dataDecrypterType,
};
}
}
public MethodDefinition Method {
get { return stringMethod; }
}
public bool Detected {
get { return stringType != null; }
}
public StringDecrypter(ModuleDefinition module, DecrypterType decrypterType) {
this.module = module;
this.decrypterType = decrypterType;
}
public void find() {
foreach (var type in module.Types) {
if (!checkType(type))
continue;
foreach (var method in type.Methods) {
if (!checkDecrypterMethod(method))
continue;
stringType = type;
stringMethod = method;
return;
}
}
}
static string[] requiredFieldTypes = new string[] {
"System.Byte[]",
"System.Int16",
};
bool checkType(TypeDefinition type) {
if (!new FieldTypes(type).all(requiredFieldTypes))
return false;
if (type.NestedTypes.Count == 0) {
return DotNetUtils.findFieldType(type, "System.IO.BinaryReader", true) != null &&
DotNetUtils.findFieldType(type, "System.Collections.Generic.Dictionary`2", true) != null;
}
else if (type.NestedTypes.Count == 3) {
streamHelperType = findStreamHelperType(type);
return streamHelperType != null;
}
else if (type.NestedTypes.Count == 1) {
return type.NestedTypes[0].IsEnum;
}
else
return false;
}
static string[] streamHelperTypeFields = new string[] {
"System.IO.Stream",
"System.Byte[]",
};
static StreamHelperType findStreamHelperType(TypeDefinition type) {
foreach (var field in type.Fields) {
var nested = field.FieldType as TypeDefinition;
if (nested == null)
continue;
if (nested.DeclaringType != type)
continue;
if (!new FieldTypes(nested).exactly(streamHelperTypeFields))
continue;
var streamHelperType = new StreamHelperType(nested);
if (!streamHelperType.Detected)
continue;
return streamHelperType;
}
return null;
}
static string[] requiredLocalTypes = new string[] {
"System.Boolean",
"System.Byte[]",
"System.Char[]",
"System.Int16",
"System.Int32",
"System.Reflection.Assembly",
"System.String",
};
static bool checkDecrypterMethod(MethodDefinition method) {
if (method == null || !method.IsStatic || method.Body == null)
return false;
if (!DotNetUtils.isMethod(method, "System.String", "(System.Int32)"))
return false;
if (!new LocalTypes(method).all(requiredLocalTypes))
return false;
foreach (var instr in method.Body.Instructions) {
if (instr.OpCode != OpCodes.Callvirt)
continue;
var calledMethod = instr.Operand as MethodReference;
if (calledMethod != null && calledMethod.FullName == "System.IO.Stream System.Reflection.Assembly::GetManifestResourceStream(System.String)")
return true;
}
return false;
}
public void initialize(ISimpleDeobfuscator simpleDeobfuscator) {
if (stringType == null)
return;
if (!findConstants(simpleDeobfuscator)) {
if (encryptedResource == null)
Log.w("Could not find encrypted resource. Strings cannot be decrypted.");
else
Log.w("Can't decrypt strings. Possibly a new Eazfuscator.NET version.");
return;
}
}
bool findConstants(ISimpleDeobfuscator simpleDeobfuscator) {
if (!findResource(stringMethod))
return false;
simpleDeobfuscator.deobfuscate(stringMethod);
checkMinus2 = DeobUtils.hasInteger(stringMethod, -2);
usePublicKeyToken = callsGetPublicKeyToken(stringMethod);
var int64Method = findInt64Method(stringMethod);
if (int64Method != null)
decrypterType.Type = int64Method.DeclaringType;
if (!findShorts(stringMethod))
return false;
if (!findInt3(stringMethod))
return false;
if (!findInt4(stringMethod))
return false;
if (checkMinus2 && !findInt5(stringMethod))
return false;
dataDecrypterType = findDataDecrypterType(stringMethod);
if (dataDecrypterType == null)
return false;
if (decrypterType.Detected) {
bool initializedAll;
if (!findInts(stringMethod, out initializedAll))
return false;
var cctor = DotNetUtils.getMethod(stringType, ".cctor");
if (!initializedAll && cctor != null) {
simpleDeobfuscator.deobfuscate(cctor);
if (!findIntsCctor(cctor))
return false;
}
if (!decrypterType.initialize())
return false;
}
initialize();
return true;
}
void initialize() {
reader = new BinaryReader(encryptedResource.GetResourceStream());
short len = (short)(reader.ReadInt16() ^ s1);
if (len != 0)
theKey = reader.ReadBytes(len);
else
keyLen = reader.ReadInt16() ^ s2;
if (decrypterType.Detected)
magic1 = (int)decrypterType.getMagic() ^ i1 ^ i2;
}
public string decrypt(int val) {
while (true) {
int offset = magic1 ^ i3 ^ val;
reader.BaseStream.Position = offset;
byte[] tmpKey;
if (theKey == null) {
tmpKey = reader.ReadBytes(keyLen == -1 ? (short)(reader.ReadInt16() ^ s3 ^ offset) : keyLen);
if (decrypterType.Detected) {
for (int i = 0; i < tmpKey.Length; i++)
tmpKey[i] ^= (byte)(magic1 >> ((i & 3) << 3));
}
}
else
tmpKey = theKey;
int flags = i4 ^ magic1 ^ offset ^ reader.ReadInt32();
if (checkMinus2 && flags == -2) {
var ary2 = reader.ReadBytes(4);
val = -(magic1 ^ i5) ^ (ary2[2] | (ary2[0] << 8) | (ary2[3] << 16) | (ary2[1] << 24));
continue;
}
var bytes = reader.ReadBytes(flags & 0x1FFFFFFF);
decrypt1(bytes, tmpKey);
var pkt = module.Assembly.Name.PublicKeyToken;
if (usePublicKeyToken && pkt != null && pkt.Length != 0) {
for (int i = 0; i < bytes.Length; i++)
bytes[i] ^= (byte)((pkt[i & 7] >> 5) + (pkt[i & 7] << 3));
}
if ((flags & 0x40000000) != 0)
bytes = rld(bytes);
if ((flags & 0x80000000) != 0) {
var sb = new StringBuilder(bytes.Length);
foreach (var b in bytes)
sb.Append((char)b);
return sb.ToString();
}
else
return Encoding.Unicode.GetString(bytes);
}
}
static byte[] rld(byte[] src) {
var dst = new byte[src[2] + (src[3] << 8) + (src[0] << 16) + (src[1] << 24)];
int srcIndex = 4;
int dstIndex = 0;
int flags = 0;
int bit = 128;
while (dstIndex < dst.Length) {
bit <<= 1;
if (bit == 256) {
bit = 1;
flags = src[srcIndex++];
}
if ((flags & bit) == 0) {
dst[dstIndex++] = src[srcIndex++];
continue;
}
int numBytes = (src[srcIndex] >> 2) + 3;
int copyIndex = dstIndex - ((src[srcIndex + 1] + (src[srcIndex] << 8)) & 0x3FF);
if (copyIndex < 0)
break;
while (dstIndex < dst.Length && numBytes-- > 0)
dst[dstIndex++] = dst[copyIndex++];
srcIndex += 2;
}
return dst;
}
static void decrypt1(byte[] dest, byte[] key) {
byte b = (byte)((key[1] + 7) ^ (dest.Length + 11));
uint lcg = (uint)((key[0] | (key[2] << 8)) + (b << 3));
b += 3;
ushort xn = 0;
for (int i = 0; i < dest.Length; i++) {
if ((i & 1) == 0) {
lcg = lcgNext(lcg);
xn = (ushort)(lcg >> 16);
}
byte tmp = dest[i];
dest[i] ^= (byte)(key[1] ^ xn ^ b);
b = (byte)(tmp + 3);
xn >>= 8;
}
}
static uint lcgNext(uint lcg) {
return lcg * 214013 + 2531011;
}
bool findResource(MethodDefinition method) {
encryptedResource = DotNetUtils.getResource(module, DotNetUtils.getCodeStrings(method)) as EmbeddedResource;
return encryptedResource != null;
}
static MethodDefinition findInt64Method(MethodDefinition method) {
foreach (var instr in method.Body.Instructions) {
if (instr.OpCode.Code != Code.Call)
continue;
var calledMethod = instr.Operand as MethodDefinition;
if (calledMethod == null)
continue;
if (!DotNetUtils.isMethod(calledMethod, "System.Int64", "()"))
continue;
return calledMethod;
}
return null;
}
static TypeDefinition findDataDecrypterType(MethodDefinition method) {
foreach (var instr in method.Body.Instructions) {
if (instr.OpCode.Code != Code.Call)
continue;
var calledMethod = instr.Operand as MethodDefinition;
if (calledMethod == null)
continue;
if (!DotNetUtils.isMethod(calledMethod, "System.Byte[]", "(System.Byte[],System.Byte[])"))
continue;
return calledMethod.DeclaringType;
}
return null;
}
bool findShorts(MethodDefinition method) {
int index = 0;
if (!findShort(method, ref index, ref s1))
return false;
if (!findShort(method, ref index, ref s2))
return false;
if (!findShort(method, ref index, ref s3))
return false;
return true;
}
bool findShort(MethodDefinition method, ref int index, ref short s) {
if (!findCallReadInt16(method, ref index))
return false;
index++;
return EfUtils.getInt16(method, ref index, ref s);
}
bool findInts(MethodDefinition method, out bool initializedAll) {
initializedAll = false;
// <= 3.2
int index = findIndexInt64Method_v1(method);
if (index >= 0) {
if (!EfUtils.getNextInt32(method, ref index, out i1))
return false;
int tmp;
if (!EfUtils.getNextInt32(method, ref index, out tmp))
return false;
if (!EfUtils.getNextInt32(method, ref index, out i2))
return false;
initializedAll = true;
return true;
}
// 3.3
index = findIndexInt64Method_v2(method);
if (index >= 0) {
if (!EfUtils.getNextInt32(method, ref index, out i2))
return false;
return true;
}
return false;
}
bool findIntsCctor(MethodDefinition cctor) {
int index = 0;
if (!findCallGetFrame(cctor, ref index))
return false;
int tmp1, tmp2, tmp3;
if (!EfUtils.getNextInt32(cctor, ref index, out tmp1))
return false;
if (!EfUtils.getNextInt32(cctor, ref index, out tmp2))
return false;
index = 0;
while (true) {
if (!EfUtils.getNextInt32(cctor, ref index, out tmp3))
return false;
int nextIndex = index;
int tmp4;
if (!EfUtils.getNextInt32(cctor, ref index, out tmp4))
return false;
if (tmp4 == 16)
break;
index = nextIndex;
}
i1 = tmp1 ^ tmp2 ^ tmp3;
return true;
}
bool findInt3(MethodDefinition method) {
if (!decrypterType.Detected)
return findInt3Old(method);
return findInt3New(method);
}
// <= 3.1
bool findInt3Old(MethodDefinition method) {
var instrs = method.Body.Instructions;
for (int i = 0; i < instrs.Count - 4; i++) {
var ldarg0 = instrs[i];
if (ldarg0.OpCode.Code != Code.Ldarg_0)
continue;
var ldci4 = instrs[i + 1];
if (!DotNetUtils.isLdcI4(ldci4))
continue;
int index = i + 1;
int value;
if (!EfUtils.getInt32(method, ref index, out value))
continue;
if (index >= instrs.Count)
continue;
if (instrs[index].OpCode.Code != Code.Xor)
continue;
i3 = value;
return true;
}
return false;
}
// 3.2+
bool findInt3New(MethodDefinition method) {
var instrs = method.Body.Instructions;
for (int i = 0; i < instrs.Count - 4; i++) {
var ldarg0 = instrs[i];
if (ldarg0.OpCode.Code != Code.Ldarg_0)
continue;
var ldci4 = instrs[i + 1];
if (!DotNetUtils.isLdcI4(ldci4))
continue;
if (instrs[i + 2].OpCode.Code != Code.Xor)
continue;
if (!DotNetUtils.isLdloc(instrs[i + 3]))
continue;
if (instrs[i + 4].OpCode.Code != Code.Xor)
continue;
i3 = DotNetUtils.getLdcI4Value(ldci4);
return true;
}
return false;
}
bool findInt4(MethodDefinition method) {
int index = 0;
if (!findCallReadInt32(method, ref index))
return false;
if (!EfUtils.getNextInt32(method, ref index, out i4))
return false;
return true;
}
bool findInt5(MethodDefinition method) {
int index = -1;
while (true) {
index++;
if (!findCallReadBytes(method, ref index))
return false;
if (index <= 0)
continue;
var ldci4 = method.Body.Instructions[index - 1];
if (!DotNetUtils.isLdcI4(ldci4))
continue;
if (DotNetUtils.getLdcI4Value(ldci4) != 4)
continue;
if (!EfUtils.getNextInt32(method, ref index, out i5))
return false;
return true;
}
}
static int findIndexInt64Method_v1(MethodDefinition method) {
var instrs = method.Body.Instructions;
for (int i = 0; i < instrs.Count - 2; i++) {
var ldci4 = instrs[i];
if (!DotNetUtils.isLdcI4(ldci4))
continue;
var stloc = instrs[i + 1];
if (!DotNetUtils.isStloc(stloc))
continue;
var call = instrs[i + 2];
if (call.OpCode.Code != Code.Call)
continue;
var calledMethod = call.Operand as MethodDefinition;
if (calledMethod == null)
continue;
if (!DotNetUtils.isMethod(calledMethod, "System.Int64", "()"))
continue;
return i;
}
return -1;
}
static int findIndexInt64Method_v2(MethodDefinition method) {
var instrs = method.Body.Instructions;
for (int i = 0; i < instrs.Count; i++) {
var call = instrs[i];
if (call.OpCode.Code != Code.Call)
continue;
var calledMethod = call.Operand as MethodDefinition;
if (calledMethod == null)
continue;
if (!DotNetUtils.isMethod(calledMethod, "System.Int64", "()"))
continue;
return i;
}
return -1;
}
static bool callsGetPublicKeyToken(MethodDefinition method) {
int index = 0;
return findCall(method, ref index, "System.Byte[] System.Reflection.AssemblyName::GetPublicKeyToken()");
}
bool findCallReadInt16(MethodDefinition method, ref int index) {
return findCall(method, ref index, streamHelperType == null ? "System.Int16 System.IO.BinaryReader::ReadInt16()" : streamHelperType.readInt16Method.FullName);
}
bool findCallReadInt32(MethodDefinition method, ref int index) {
return findCall(method, ref index, streamHelperType == null ? "System.Int32 System.IO.BinaryReader::ReadInt32()" : streamHelperType.readInt32Method.FullName);
}
bool findCallReadBytes(MethodDefinition method, ref int index) {
return findCall(method, ref index, streamHelperType == null ? "System.Byte[] System.IO.BinaryReader::ReadBytes(System.Int32)" : streamHelperType.readBytesMethod.FullName);
}
static bool findCallGetFrame(MethodDefinition method, ref int index) {
return findCall(method, ref index, "System.Diagnostics.StackFrame System.Diagnostics.StackTrace::GetFrame(System.Int32)");
}
static bool findCall(MethodDefinition method, ref int index, string methodFullName) {
for (; index < method.Body.Instructions.Count; index++) {
if (!findCallvirt(method, ref index))
return false;
var calledMethod = method.Body.Instructions[index].Operand as MethodReference;
if (calledMethod == null)
continue;
if (calledMethod.ToString() != methodFullName)
continue;
return true;
}
return false;
}
static bool findCallvirt(MethodDefinition method, ref int index) {
var instrs = method.Body.Instructions;
for (; index < instrs.Count; index++) {
var instr = instrs[index];
if (instr.OpCode.Code != Code.Callvirt)
continue;
return true;
}
return false;
}
}
}