109 lines
3.5 KiB
C#
109 lines
3.5 KiB
C#
/*
|
|
Copyright (C) 2011 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.Collections.Generic;
|
|
using Mono.Cecil;
|
|
using Mono.Cecil.Cil;
|
|
using de4dot.blocks;
|
|
|
|
namespace de4dot.code.deobfuscators.Dotfuscator {
|
|
class StringDecrypter {
|
|
ModuleDefinition module;
|
|
Dictionary<MethodReference, StringDecrypterInfo> stringDecrypterMethods = new Dictionary<MethodReference, StringDecrypterInfo>();
|
|
|
|
public class StringDecrypterInfo {
|
|
public MethodDefinition method;
|
|
public int magic;
|
|
public StringDecrypterInfo(MethodDefinition method, int magic) {
|
|
this.method = method;
|
|
this.magic = magic;
|
|
}
|
|
}
|
|
|
|
public bool Detected {
|
|
get { return stringDecrypterMethods.Count > 0; }
|
|
}
|
|
|
|
public IEnumerable<MethodDefinition> StringDecrypters {
|
|
get {
|
|
var list = new List<MethodDefinition>(stringDecrypterMethods.Count);
|
|
foreach (var info in stringDecrypterMethods)
|
|
list.Add(info.Value.method);
|
|
return list;
|
|
}
|
|
}
|
|
|
|
public IEnumerable<StringDecrypterInfo> StringDecrypterInfos {
|
|
get { return stringDecrypterMethods.Values; }
|
|
}
|
|
|
|
public StringDecrypter(ModuleDefinition module) {
|
|
this.module = module;
|
|
}
|
|
|
|
public void find(ISimpleDeobfuscator simpleDeobfuscator) {
|
|
foreach (var type in module.GetTypes())
|
|
findStringDecrypterMethods(type, simpleDeobfuscator);
|
|
}
|
|
|
|
void findStringDecrypterMethods(TypeDefinition type, ISimpleDeobfuscator simpleDeobfuscator) {
|
|
foreach (var method in DotNetUtils.findMethods(type.Methods, "System.String", new string[] { "System.String", "System.Int32" })) {
|
|
if (method.Body.HasExceptionHandlers)
|
|
continue;
|
|
|
|
var methodCalls = DotNetUtils.getMethodCallCounts(method);
|
|
if (methodCalls.count("System.Char[] System.String::ToCharArray()") != 1)
|
|
continue;
|
|
if (methodCalls.count("System.String System.String::Intern(System.String)") != 1)
|
|
continue;
|
|
|
|
simpleDeobfuscator.deobfuscate(method);
|
|
var instructions = method.Body.Instructions;
|
|
for (int i = 0; i <= instructions.Count - 3; i++) {
|
|
var ldci4 = method.Body.Instructions[i];
|
|
if (!DotNetUtils.isLdcI4(ldci4))
|
|
continue;
|
|
if (instructions[i + 1].OpCode.Code != Code.Ldarg_1)
|
|
continue;
|
|
if (instructions[i + 2].OpCode.Code != Code.Add)
|
|
continue;
|
|
|
|
var info = new StringDecrypterInfo(method, DotNetUtils.getLdcI4Value(ldci4));
|
|
stringDecrypterMethods[info.method] = info;
|
|
Log.v("Found string decrypter method: {0}, magic: 0x{1:X8}", Utils.removeNewlines(info.method), info.magic);
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
public string decrypt(MethodReference method, string encrypted, int value) {
|
|
var info = stringDecrypterMethods[method];
|
|
char[] chars = encrypted.ToCharArray();
|
|
byte key = (byte)(info.magic + value);
|
|
for (int i = 0; i < chars.Length; i++) {
|
|
char c = chars[i];
|
|
byte b1 = (byte)((byte)c ^ key++);
|
|
byte b2 = (byte)((byte)(c >> 8) ^ key++);
|
|
chars[i] = (char)((b1 << 8) | b2);
|
|
}
|
|
return new string(chars);
|
|
}
|
|
}
|
|
}
|