129 lines
3.4 KiB
C#
129 lines
3.4 KiB
C#
/*
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Copyright (C) 2011-2015 de4dot@gmail.com
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This file is part of de4dot.
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de4dot is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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de4dot is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with de4dot. If not, see <http://www.gnu.org/licenses/>.
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*/
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using System;
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using System.Collections.Generic;
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using System.Text;
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using dnlib.DotNet;
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using de4dot.blocks;
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namespace de4dot.code.deobfuscators.MaxtoCode {
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class StringDecrypter {
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DecrypterInfo decrypterInfo;
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MethodDef decryptMethod;
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string[] decryptedStrings;
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Encoding encoding;
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public MethodDef Method {
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get { return decryptMethod; }
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}
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public bool Detected {
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get { return decryptMethod != null; }
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}
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public StringDecrypter(DecrypterInfo decrypterInfo) {
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this.decrypterInfo = decrypterInfo;
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}
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public void Find() {
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if (decrypterInfo == null)
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return;
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decryptMethod = FindDecryptMethod(decrypterInfo.mainType.Type);
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if (decryptMethod == null)
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return;
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}
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static MethodDef FindDecryptMethod(TypeDef type) {
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if (type == null)
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return null;
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foreach (var method in type.Methods) {
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if (method.Body == null || !method.IsStatic || method.IsPrivate)
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continue;
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if (!DotNetUtils.IsMethod(method, "System.String", "(System.UInt32)"))
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continue;
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if (!DotNetUtils.CallsMethod(method, "System.String System.Runtime.InteropServices.Marshal::PtrToStringAnsi(System.IntPtr)"))
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continue;
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return method;
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}
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return null;
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}
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public void Initialize(Encoding encoding) {
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this.encoding = encoding;
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}
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void InitializeStrings() {
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if (decryptedStrings != null)
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return;
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var peImage = decrypterInfo.peImage;
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var peHeader = decrypterInfo.peHeader;
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var mcKey = decrypterInfo.mcKey;
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var fileData = decrypterInfo.fileData;
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var stringsRva = peHeader.GetRva(0x0AF0, mcKey.ReadUInt32(0x46));
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if (stringsRva == 0)
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return;
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int stringsOffset = (int)peImage.RvaToOffset(stringsRva);
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int numStrings = peImage.ReadInt32(stringsRva) ^ (int)mcKey.ReadUInt32(0);
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decryptedStrings = new string[numStrings];
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for (int i = 0, ki = 2, soffs = stringsOffset + 4; i < numStrings; i++) {
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int stringLen = BitConverter.ToInt32(fileData, soffs) ^ (int)mcKey.ReadUInt32(ki);
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ki += 2;
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if (ki >= 0x1FF0)
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ki = 0;
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soffs += 4;
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var bytes = new byte[stringLen];
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for (int j = 0; j < stringLen; j++, soffs++) {
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byte b = (byte)(fileData[soffs] ^ mcKey.ReadByte(ki));
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ki = Add(ki, 1);
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bytes[j] = b;
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}
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decryptedStrings[i] = Decode(bytes);
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}
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}
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string Decode(byte[] bytes) {
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string s = encoding.GetString(bytes);
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int len = s.Length;
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if (len == 0 || s[len - 1] != 0)
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return s;
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for (; len > 0; len--) {
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if (s[len - 1] != 0)
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break;
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}
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if (len <= 0)
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return string.Empty;
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return s.Substring(0, len);
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}
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static int Add(int ki, int size) {
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return (ki + size) % 0x1FF0;
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}
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public string Decrypt(uint id) {
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InitializeStrings();
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return decryptedStrings[(int)id - 1];
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}
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}
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}
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