496 lines
14 KiB
C#
496 lines
14 KiB
C#
/*
|
|
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 <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
using System;
|
|
using System.Collections.Generic;
|
|
using System.Text;
|
|
using Mono.Cecil;
|
|
using Mono.Cecil.Cil;
|
|
using de4dot.blocks;
|
|
|
|
namespace de4dot.code.deobfuscators.DeepSea {
|
|
class StringDecrypter {
|
|
ModuleDefinition module;
|
|
MethodDefinitionAndDeclaringTypeDict<IDecrypterInfo> methodToInfo = new MethodDefinitionAndDeclaringTypeDict<IDecrypterInfo>();
|
|
|
|
interface IDecrypterInfo {
|
|
MethodDefinition Method { get; }
|
|
string decrypt(object[] args);
|
|
void cleanup();
|
|
}
|
|
|
|
static short[] findKey(MethodDefinition initMethod, FieldDefinition keyField) {
|
|
var instrs = initMethod.Body.Instructions;
|
|
for (int i = 0; i < instrs.Count - 2; i++) {
|
|
var ldci4 = instrs[i];
|
|
if (!DotNetUtils.isLdcI4(ldci4))
|
|
continue;
|
|
var newarr = instrs[i + 1];
|
|
if (newarr.OpCode.Code != Code.Newarr)
|
|
continue;
|
|
if (newarr.Operand.ToString() != "System.Char")
|
|
continue;
|
|
|
|
var stloc = instrs[i + 2];
|
|
if (!DotNetUtils.isStloc(stloc))
|
|
continue;
|
|
var local = DotNetUtils.getLocalVar(initMethod.Body.Variables, stloc);
|
|
|
|
int startInitIndex = i;
|
|
i++;
|
|
var array = ArrayFinder.getInitializedInt16Array(DotNetUtils.getLdcI4Value(ldci4), initMethod, ref i);
|
|
if (array == null)
|
|
continue;
|
|
|
|
var field = getStoreField(initMethod, startInitIndex, local);
|
|
if (field == null)
|
|
continue;
|
|
if (MemberReferenceHelper.compareFieldReferenceAndDeclaringType(keyField, field))
|
|
return array;
|
|
}
|
|
|
|
return null;
|
|
}
|
|
|
|
static FieldDefinition getStoreField(MethodDefinition method, int startIndex, VariableDefinition local) {
|
|
var instrs = method.Body.Instructions;
|
|
for (int i = 0; i < instrs.Count - 1; i++) {
|
|
var ldloc = instrs[i];
|
|
if (!DotNetUtils.isLdloc(ldloc))
|
|
continue;
|
|
if (DotNetUtils.getLocalVar(method.Body.Variables, ldloc) != local)
|
|
continue;
|
|
|
|
var stsfld = instrs[i + 1];
|
|
if (stsfld.OpCode.Code != Code.Stsfld)
|
|
continue;
|
|
return stsfld.Operand as FieldDefinition;
|
|
}
|
|
|
|
return null;
|
|
}
|
|
|
|
class DecrypterInfo4 : IDecrypterInfo {
|
|
MethodDefinition cctor;
|
|
public MethodDefinition Method { get; set; }
|
|
int magic;
|
|
FieldDefinition cachedStringsField;
|
|
FieldDefinition keyField;
|
|
FieldDefinition encryptedStringsField;
|
|
FieldDefinition encryptedDataField;
|
|
short[] key;
|
|
ushort[] encryptedData;
|
|
|
|
public DecrypterInfo4(MethodDefinition cctor, MethodDefinition method) {
|
|
this.cctor = cctor;
|
|
this.Method = method;
|
|
}
|
|
|
|
public bool initialize() {
|
|
if (!findMagic(Method, out magic))
|
|
return false;
|
|
|
|
var charArrayFields = findFields();
|
|
if (charArrayFields == null || charArrayFields.Count != 2)
|
|
return false;
|
|
|
|
encryptedStringsField = findEncryptedStrings(cctor, charArrayFields, out encryptedDataField);
|
|
if (encryptedStringsField == null)
|
|
return false;
|
|
if (encryptedDataField.InitialValue.Length % 2 == 1)
|
|
return false;
|
|
encryptedData = new ushort[encryptedDataField.InitialValue.Length / 2];
|
|
Buffer.BlockCopy(encryptedDataField.InitialValue, 0, encryptedData, 0, encryptedDataField.InitialValue.Length);
|
|
|
|
charArrayFields.Remove(encryptedStringsField);
|
|
keyField = charArrayFields[0];
|
|
|
|
key = findKey();
|
|
if (key == null || key.Length == 0)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
static bool findMagic(MethodDefinition method, out int magic) {
|
|
var instrs = method.Body.Instructions;
|
|
for (int i = 0; i < instrs.Count - 2; i++) {
|
|
var ldarg = instrs[i];
|
|
if (DotNetUtils.getArgIndex(ldarg) < 0)
|
|
continue;
|
|
var ldci4 = instrs[i + 1];
|
|
if (!DotNetUtils.isLdcI4(ldci4))
|
|
continue;
|
|
if (instrs[i + 2].OpCode.Code != Code.Xor)
|
|
continue;
|
|
magic = DotNetUtils.getLdcI4Value(ldci4);
|
|
return true;
|
|
}
|
|
magic = 0;
|
|
return false;
|
|
}
|
|
|
|
List<FieldDefinition> findFields() {
|
|
var charArrayFields = new List<FieldDefinition>();
|
|
|
|
foreach (var instr in Method.Body.Instructions) {
|
|
if (instr.OpCode.Code != Code.Stsfld && instr.OpCode.Code != Code.Ldsfld)
|
|
continue;
|
|
var field = instr.Operand as FieldDefinition;
|
|
if (field == null)
|
|
continue;
|
|
if (!MemberReferenceHelper.compareTypes(Method.DeclaringType, field.DeclaringType))
|
|
continue;
|
|
switch (field.FieldType.FullName) {
|
|
case "System.Char[]":
|
|
if (!charArrayFields.Contains(field))
|
|
charArrayFields.Add(field);
|
|
break;
|
|
|
|
case "System.String[]":
|
|
if (cachedStringsField != null && cachedStringsField != field)
|
|
return null;
|
|
cachedStringsField = field;
|
|
break;
|
|
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (cachedStringsField == null)
|
|
return null;
|
|
|
|
return charArrayFields;
|
|
}
|
|
|
|
static FieldDefinition findEncryptedStrings(MethodDefinition initMethod, List<FieldDefinition> ourFields, out FieldDefinition dataField) {
|
|
for (int i = 0; i < initMethod.Body.Instructions.Count; i++) {
|
|
var instrs = DotNetUtils.getInstructions(initMethod.Body.Instructions, i, OpCodes.Ldtoken, OpCodes.Call, OpCodes.Stsfld);
|
|
if (instrs == null)
|
|
continue;
|
|
|
|
dataField = instrs[0].Operand as FieldDefinition;
|
|
if (dataField == null || dataField.InitialValue == null || dataField.InitialValue.Length == 0)
|
|
continue;
|
|
|
|
var savedField = instrs[2].Operand as FieldDefinition;
|
|
if (savedField == null || !matches(ourFields, savedField))
|
|
continue;
|
|
|
|
return savedField;
|
|
}
|
|
|
|
dataField = null;
|
|
return null;
|
|
}
|
|
|
|
static bool matches(IEnumerable<FieldDefinition> ourFields, FieldReference field) {
|
|
foreach (var ourField in ourFields) {
|
|
if (MemberReferenceHelper.compareFieldReferenceAndDeclaringType(ourField, field))
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
short[] findKey() {
|
|
var pkt = cctor.Module.Assembly.Name.PublicKeyToken;
|
|
if (pkt != null && pkt.Length > 0)
|
|
return getPublicKeyTokenKey(pkt);
|
|
return findKey(cctor);
|
|
}
|
|
|
|
short[] findKey(MethodDefinition initMethod) {
|
|
return StringDecrypter.findKey(initMethod, keyField);
|
|
}
|
|
|
|
static short[] getPublicKeyTokenKey(byte[] publicKeyToken) {
|
|
var key = new short[publicKeyToken.Length];
|
|
for (int i = 0; i < publicKeyToken.Length; i++) {
|
|
int b = publicKeyToken[i];
|
|
key[i] = (short)((b << 4) ^ b);
|
|
}
|
|
return key;
|
|
}
|
|
|
|
public string decrypt(object[] args) {
|
|
return decrypt((int)args[0], (int)args[1]);
|
|
}
|
|
|
|
string decrypt(int magic2, int magic3) {
|
|
int index = magic ^ magic2 ^ magic3;
|
|
int cachedIndex = (ushort)encryptedData[index++];
|
|
int stringLen = (int)(ushort)encryptedData[index++] + ((int)(ushort)encryptedData[index++] << 16);
|
|
var sb = new StringBuilder(stringLen);
|
|
for (int i = 0; i < stringLen; i++)
|
|
sb.Append((char)(encryptedData[index++] ^ key[cachedIndex++ % key.Length]));
|
|
return sb.ToString();
|
|
}
|
|
|
|
public void cleanup() {
|
|
encryptedDataField.InitialValue = new byte[0];
|
|
}
|
|
}
|
|
|
|
class DecrypterInfo3 : IDecrypterInfo {
|
|
MethodDefinition cctor;
|
|
public MethodDefinition Method { get; set; }
|
|
FieldDefinition cachedStringsField;
|
|
FieldDefinition keyField;
|
|
int magic;
|
|
string[] encryptedStrings;
|
|
short[] key;
|
|
public DecrypterInfo3(MethodDefinition cctor, MethodDefinition method) {
|
|
this.cctor = cctor;
|
|
this.Method = method;
|
|
}
|
|
|
|
public string decrypt(object[] args) {
|
|
return decrypt((int)args[0]);
|
|
}
|
|
|
|
string decrypt(int magic2) {
|
|
var es = encryptedStrings[magic ^ magic2];
|
|
var sb = new StringBuilder(es.Length);
|
|
for (int i = 0; i < es.Length; i++)
|
|
sb.Append((char)(es[i] ^ key[(magic2 + i) % key.Length]));
|
|
return sb.ToString();
|
|
}
|
|
|
|
public bool initialize() {
|
|
if (!findMagic(Method, out magic))
|
|
return false;
|
|
|
|
if (!findFields())
|
|
return false;
|
|
|
|
if (!findEncryptedStrings(Method))
|
|
return false;
|
|
|
|
key = findKey();
|
|
if (key.Length == 0)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
bool findFields() {
|
|
foreach (var instr in Method.Body.Instructions) {
|
|
if (instr.OpCode.Code != Code.Stsfld && instr.OpCode.Code != Code.Ldsfld)
|
|
continue;
|
|
var field = instr.Operand as FieldDefinition;
|
|
if (field == null)
|
|
continue;
|
|
if (!MemberReferenceHelper.compareTypes(Method.DeclaringType, field.DeclaringType))
|
|
continue;
|
|
switch (field.FieldType.FullName) {
|
|
case "System.Char[]":
|
|
if (keyField != null && keyField != field)
|
|
return false;
|
|
keyField = field;
|
|
break;
|
|
|
|
case "System.String[]":
|
|
if (cachedStringsField != null && cachedStringsField != field)
|
|
return false;
|
|
cachedStringsField = field;
|
|
break;
|
|
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
|
|
return keyField != null && cachedStringsField != null;
|
|
}
|
|
|
|
short[] findKey() {
|
|
var pkt = cctor.Module.Assembly.Name.PublicKeyToken;
|
|
if (pkt != null && pkt.Length > 0)
|
|
return getPublicKeyTokenKey(pkt);
|
|
return findKey(cctor);
|
|
}
|
|
|
|
short[] findKey(MethodDefinition initMethod) {
|
|
return StringDecrypter.findKey(initMethod, keyField);
|
|
}
|
|
|
|
static short[] getPublicKeyTokenKey(byte[] publicKeyToken) {
|
|
var key = new short[publicKeyToken.Length];
|
|
for (int i = 0; i < publicKeyToken.Length; i++) {
|
|
int b = publicKeyToken[i];
|
|
key[i] = (short)((b << 4) ^ b);
|
|
}
|
|
return key;
|
|
}
|
|
|
|
static bool findMagic(MethodDefinition method, out int magic) {
|
|
var instrs = method.Body.Instructions;
|
|
for (int i = 0; i < instrs.Count - 2; i++) {
|
|
var ldarg = instrs[i];
|
|
if (DotNetUtils.getArgIndex(ldarg) < 0)
|
|
continue;
|
|
var ldci4 = instrs[i + 1];
|
|
if (!DotNetUtils.isLdcI4(ldci4))
|
|
continue;
|
|
if (instrs[i + 2].OpCode.Code != Code.Xor)
|
|
continue;
|
|
magic = DotNetUtils.getLdcI4Value(ldci4);
|
|
return true;
|
|
}
|
|
magic = 0;
|
|
return false;
|
|
}
|
|
|
|
bool findEncryptedStrings(MethodDefinition method) {
|
|
var switchInstr = getOnlySwitchInstruction(method);
|
|
if (switchInstr == null)
|
|
return false;
|
|
var targets = (Instruction[])switchInstr.Operand;
|
|
encryptedStrings = new string[targets.Length];
|
|
for (int i = 0; i < targets.Length; i++) {
|
|
var target = targets[i];
|
|
if (target.OpCode.Code != Code.Ldstr)
|
|
return false;
|
|
encryptedStrings[i] = (string)target.Operand;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
static Instruction getOnlySwitchInstruction(MethodDefinition method) {
|
|
Instruction switchInstr = null;
|
|
foreach (var instr in method.Body.Instructions) {
|
|
if (instr.OpCode.Code != Code.Switch)
|
|
continue;
|
|
if (switchInstr != null)
|
|
return null;
|
|
switchInstr = instr;
|
|
}
|
|
return switchInstr;
|
|
}
|
|
|
|
public void cleanup() {
|
|
}
|
|
|
|
public override string ToString() {
|
|
return string.Format("M:{0:X8} N:{1}", magic, encryptedStrings.Length);
|
|
}
|
|
}
|
|
|
|
public bool Detected {
|
|
get { return methodToInfo.Count != 0; }
|
|
}
|
|
|
|
public List<MethodDefinition> DecrypterMethods {
|
|
get {
|
|
var methods = new List<MethodDefinition>(methodToInfo.Count);
|
|
foreach (var info in methodToInfo.getValues())
|
|
methods.Add(info.Method);
|
|
return methods;
|
|
}
|
|
}
|
|
|
|
public StringDecrypter(ModuleDefinition module) {
|
|
this.module = module;
|
|
}
|
|
|
|
public void find(ISimpleDeobfuscator simpleDeobfuscator) {
|
|
bool hasPublicKeyToken = module.Assembly.Name.PublicKeyToken != null && module.Assembly.Name.PublicKeyToken.Length != 0;
|
|
foreach (var type in module.GetTypes()) {
|
|
if (!checkFields(type.Fields))
|
|
continue;
|
|
var cctor = DotNetUtils.getMethod(type, ".cctor");
|
|
if (cctor == null)
|
|
continue;
|
|
if (!hasPublicKeyToken)
|
|
simpleDeobfuscator.deobfuscate(cctor);
|
|
|
|
foreach (var method in type.Methods) {
|
|
if (method.Body == null)
|
|
continue;
|
|
|
|
IDecrypterInfo info = null;
|
|
|
|
if (DotNetUtils.isMethod(method, "System.String", "(System.Int32)")) {
|
|
simpleDeobfuscator.deobfuscate(method);
|
|
info = getInfoV3(cctor, method);
|
|
}
|
|
else if (DotNetUtils.isMethod(method, "System.String", "(System.Int32,System.Int32)")) {
|
|
simpleDeobfuscator.deobfuscate(method);
|
|
info = getInfoV4(cctor, method);
|
|
}
|
|
|
|
if (info == null)
|
|
continue;
|
|
methodToInfo.add(method, info);
|
|
}
|
|
|
|
foreach (var method in DotNetUtils.findMethods(type.Methods, "System.String", new string[] { "System.Int32" }, true)) {
|
|
simpleDeobfuscator.deobfuscate(method);
|
|
var info = getInfoV3(cctor, method);
|
|
if (info == null)
|
|
continue;
|
|
methodToInfo.add(method, info);
|
|
}
|
|
}
|
|
}
|
|
|
|
static bool checkFields(IEnumerable<FieldDefinition> fields) {
|
|
bool foundCharAry = false, foundStringAry = false;
|
|
foreach (var field in fields) {
|
|
if (foundCharAry && foundStringAry)
|
|
break;
|
|
switch (field.FieldType.FullName) {
|
|
case "System.Char[]":
|
|
foundCharAry = true;
|
|
break;
|
|
case "System.String[]":
|
|
foundStringAry = true;
|
|
break;
|
|
}
|
|
}
|
|
return foundCharAry && foundStringAry;
|
|
}
|
|
|
|
DecrypterInfo3 getInfoV3(MethodDefinition cctor, MethodDefinition method) {
|
|
var info = new DecrypterInfo3(cctor, method);
|
|
if (!info.initialize())
|
|
return null;
|
|
return info;
|
|
}
|
|
|
|
DecrypterInfo4 getInfoV4(MethodDefinition cctor, MethodDefinition method) {
|
|
var info = new DecrypterInfo4(cctor, method);
|
|
if (!info.initialize())
|
|
return null;
|
|
return info;
|
|
}
|
|
|
|
public string decrypt(MethodReference method, object[] args) {
|
|
var info = methodToInfo.find(method);
|
|
return info.decrypt(args);
|
|
}
|
|
|
|
public void cleanup() {
|
|
foreach (var info in methodToInfo.getValues())
|
|
info.cleanup();
|
|
}
|
|
}
|
|
}
|