118 lines
3.4 KiB
C#
118 lines
3.4 KiB
C#
/*
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Copyright (C) 2011 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.IO;
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using System.IO.Compression;
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using System.Security.Cryptography;
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using Mono.Cecil;
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namespace de4dot.deobfuscators.CryptoObfuscator {
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class ResourceDecrypter {
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const int BUFLEN = 0x8000;
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ModuleDefinition module;
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byte[] buffer1 = new byte[BUFLEN];
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byte[] buffer2 = new byte[BUFLEN];
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public ResourceDecrypter(ModuleDefinition module) {
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this.module = module;
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}
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public byte[] decrypt(Stream resourceStream) {
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byte flags = (byte)resourceStream.ReadByte();
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Stream sourceStream = resourceStream;
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bool didSomething = false;
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if ((flags & 1) != 0) {
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var memStream = new MemoryStream((int)resourceStream.Length);
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using (var provider = new DESCryptoServiceProvider()) {
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var iv = new byte[8];
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sourceStream.Read(iv, 0, 8);
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provider.IV = iv;
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provider.Key = getKey(sourceStream);
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using (var transform = provider.CreateDecryptor()) {
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while (true) {
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int count = sourceStream.Read(buffer1, 0, buffer1.Length);
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if (count <= 0)
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break;
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int count2 = transform.TransformBlock(buffer1, 0, count, buffer2, 0);
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memStream.Write(buffer2, 0, count2);
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}
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var finalData = transform.TransformFinalBlock(buffer1, 0, 0);
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memStream.Write(finalData, 0, finalData.Length);
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}
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}
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sourceStream = memStream;
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didSomething = true;
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}
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if ((flags & 2) != 0) {
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var memStream = new MemoryStream((int)resourceStream.Length);
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sourceStream.Position = 0;
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using (var inflater = new DeflateStream(sourceStream, CompressionMode.Decompress)) {
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while (true) {
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int count = inflater.Read(buffer1, 0, buffer1.Length);
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if (count <= 0)
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break;
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memStream.Write(buffer1, 0, count);
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}
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}
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sourceStream = memStream;
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didSomething = true;
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}
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if ((flags & 4) != 0) {
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var memStream = new MemoryStream((int)resourceStream.Length);
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sourceStream.Position = 0;
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for (int i = 0; i < sourceStream.Length; i++)
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memStream.WriteByte((byte)~sourceStream.ReadByte());
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sourceStream = memStream;
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didSomething = true;
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}
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if (didSomething && sourceStream is MemoryStream) {
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var memStream = (MemoryStream)sourceStream;
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return memStream.ToArray();
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}
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else {
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int len = (int)(sourceStream.Length - sourceStream.Position);
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byte[] data = new byte[len];
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sourceStream.Read(data, 0, len);
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return data;
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}
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}
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byte[] getKey(Stream resourceStream) {
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byte[] key = new byte[8];
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resourceStream.Read(key, 0, key.Length);
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for (int i = 0; i < key.Length; i++) {
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if (key[i] != 0)
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return key;
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}
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key = module.Assembly.Name.PublicKeyToken;
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if (key == null)
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throw new ApplicationException("PublicKeyToken is null, can't decrypt resources");
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return key;
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}
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}
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}
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