428 lines
14 KiB
C#
428 lines
14 KiB
C#
/*
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Copyright (C) 2011-2014 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.IO;
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using dnlib.IO;
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using dnlib.DotNet;
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using dnlib.DotNet.MD;
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using dnlib.DotNet.Emit;
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using dnlib.DotNet.Writer;
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using de4dot.blocks;
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namespace de4dot.code.deobfuscators.dotNET_Reactor.v4 {
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class MethodsDecrypter {
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ModuleDefMD module;
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EncryptedResource encryptedResource;
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Dictionary<uint, byte[]> tokenToNativeMethod = new Dictionary<uint, byte[]>();
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Dictionary<MethodDef, byte[]> methodToNativeMethod = new Dictionary<MethodDef, byte[]>();
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List<MethodDef> validNativeMethods;
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int totalEncryptedNativeMethods = 0;
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long xorKey;
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public bool Detected {
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get { return encryptedResource.Method != null; }
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}
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public bool HasNativeMethods {
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get { return methodToNativeMethod.Count > 0; }
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}
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public TypeDef DecrypterType {
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get { return encryptedResource.Type; }
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}
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public MethodDef Method {
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get { return encryptedResource.Method; }
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}
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public EmbeddedResource Resource {
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get { return encryptedResource.Resource; }
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}
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public DnrDecrypterType DecrypterTypeVersion {
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get { return encryptedResource.GuessDecrypterType(); }
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}
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public MethodsDecrypter(ModuleDefMD module) {
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this.module = module;
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this.encryptedResource = new EncryptedResource(module);
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}
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public MethodsDecrypter(ModuleDefMD module, MethodsDecrypter oldOne) {
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this.module = module;
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this.encryptedResource = new EncryptedResource(module, oldOne.encryptedResource);
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this.tokenToNativeMethod = oldOne.tokenToNativeMethod;
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this.totalEncryptedNativeMethods = oldOne.totalEncryptedNativeMethods;
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this.xorKey = oldOne.xorKey;
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}
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public void Find() {
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var additionalTypes = new string[] {
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"System.IntPtr",
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// "System.Reflection.Assembly", //TODO: Not in unknown DNR version with jitter support
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};
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var checkedMethods = new Dictionary<IMethod, bool>(MethodEqualityComparer.CompareDeclaringTypes);
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var callCounter = new CallCounter();
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int typesLeft = 30;
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foreach (var type in module.GetTypes()) {
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var cctor = type.FindStaticConstructor();
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if (cctor == null || cctor.Body == null)
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continue;
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if (typesLeft-- <= 0)
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break;
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foreach (var method in DotNetUtils.GetCalledMethods(module, cctor)) {
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if (!checkedMethods.ContainsKey(method)) {
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checkedMethods[method] = false;
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if (method.DeclaringType.BaseType == null || method.DeclaringType.BaseType.FullName != "System.Object")
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continue;
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if (!DotNetUtils.IsMethod(method, "System.Void", "()"))
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continue;
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if (!encryptedResource.CouldBeResourceDecrypter(method, additionalTypes))
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continue;
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checkedMethods[method] = true;
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}
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else if (!checkedMethods[method])
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continue;
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callCounter.Add(method);
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}
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}
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encryptedResource.Method = (MethodDef)callCounter.Most();
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}
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void XorEncrypt(byte[] data) {
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if (xorKey == 0)
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return;
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var stream = new MemoryStream(data);
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var reader = new BinaryReader(stream);
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var writer = new BinaryWriter(stream);
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int count = data.Length / 8;
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for (int i = 0; i < count; i++) {
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long val = reader.ReadInt64();
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val ^= xorKey;
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stream.Position -= 8;
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writer.Write(val);
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}
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}
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readonly static short[] nativeLdci4 = new short[] { 0x55, 0x8B, 0xEC, 0xB8, -1, -1, -1, -1, 0x5D, 0xC3 };
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readonly static short[] nativeLdci4_0 = new short[] { 0x55, 0x8B, 0xEC, 0x33, 0xC0, 0x5D, 0xC3 };
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public bool Decrypt(MyPEImage peImage, ISimpleDeobfuscator simpleDeobfuscator, ref DumpedMethods dumpedMethods, Dictionary<uint, byte[]> tokenToNativeCode, bool unpackedNativeFile) {
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if (encryptedResource.Method == null)
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return false;
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encryptedResource.Initialize(simpleDeobfuscator);
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if (!encryptedResource.FoundResource)
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return false;
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var methodsData = encryptedResource.Decrypt();
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bool hooksJitter = FindDnrCompileMethod(encryptedResource.Method.DeclaringType) != null;
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xorKey = GetXorKey();
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XorEncrypt(methodsData);
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var methodsDataReader = MemoryImageStream.Create(methodsData);
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int patchCount = methodsDataReader.ReadInt32();
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int mode = methodsDataReader.ReadInt32();
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int tmp = methodsDataReader.ReadInt32();
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methodsDataReader.Position -= 4;
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if ((tmp & 0xFF000000) == 0x06000000) {
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// It's method token + rva. DNR 3.7.0.3 (and earlier?) - 3.9.0.1
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methodsDataReader.Position += 8L * patchCount;
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patchCount = methodsDataReader.ReadInt32();
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mode = methodsDataReader.ReadInt32();
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PatchDwords(peImage, methodsDataReader, patchCount);
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while (methodsDataReader.Position < methodsData.Length - 1) {
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uint token = methodsDataReader.ReadUInt32();
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int numDwords = methodsDataReader.ReadInt32();
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PatchDwords(peImage, methodsDataReader, numDwords / 2);
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}
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}
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else if (!hooksJitter || mode == 1) {
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// DNR 3.9.8.0, 4.0+
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PatchDwords(peImage, methodsDataReader, patchCount);
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bool oldCode = !IsNewer45Decryption(encryptedResource.Method);
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while (methodsDataReader.Position < methodsData.Length - 1) {
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uint rva = methodsDataReader.ReadUInt32();
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int size;
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if (oldCode) {
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methodsDataReader.ReadUInt32(); // token, unknown, or index
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size = methodsDataReader.ReadInt32();
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}
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else
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size = methodsDataReader.ReadInt32() * 4;
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var newData = methodsDataReader.ReadBytes(size);
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if (unpackedNativeFile)
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peImage.DotNetSafeWriteOffset(rva, newData);
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else
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peImage.DotNetSafeWrite(rva, newData);
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}
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}
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else {
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// DNR 4.0+ (jitter is hooked)
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var methodDef = peImage.MetaData.TablesStream.MethodTable;
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var rvaToIndex = new Dictionary<uint, int>((int)methodDef.Rows);
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uint offset = (uint)methodDef.StartOffset;
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for (int i = 0; i < methodDef.Rows; i++) {
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uint rva = peImage.OffsetReadUInt32(offset);
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offset += methodDef.RowSize;
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if (rva == 0)
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continue;
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if ((peImage.ReadByte(rva) & 3) == 2)
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rva++;
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else
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rva += (uint)(4 * (peImage.ReadByte(rva + 1) >> 4));
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rvaToIndex[rva] = i;
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}
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PatchDwords(peImage, methodsDataReader, patchCount);
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int count = methodsDataReader.ReadInt32();
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dumpedMethods = new DumpedMethods();
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while (methodsDataReader.Position < methodsData.Length - 1) {
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uint rva = methodsDataReader.ReadUInt32();
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uint index = methodsDataReader.ReadUInt32();
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bool isNativeCode = index >= 0x70000000;
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int size = methodsDataReader.ReadInt32();
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var methodData = methodsDataReader.ReadBytes(size);
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int methodIndex;
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if (!rvaToIndex.TryGetValue(rva, out methodIndex)) {
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Logger.w("Could not find method having code RVA {0:X8}", rva);
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continue;
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}
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uint methodToken = 0x06000001 + (uint)methodIndex;
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if (isNativeCode) {
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totalEncryptedNativeMethods++;
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if (tokenToNativeCode != null)
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tokenToNativeCode[methodToken] = methodData;
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// Convert return true / false methods. The others are converted to
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// throw 0xDEADCODE.
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if (DeobUtils.IsCode(nativeLdci4, methodData)) {
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uint val = BitConverter.ToUInt32(methodData, 4);
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// ldc.i4 XXXXXXXXh / ret
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methodData = new byte[] { 0x20, 0, 0, 0, 0, 0x2A };
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methodData[1] = (byte)val;
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methodData[2] = (byte)(val >> 8);
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methodData[3] = (byte)(val >> 16);
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methodData[4] = (byte)(val >> 24);
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}
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else if (DeobUtils.IsCode(nativeLdci4_0, methodData)) {
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// ldc.i4.0 / ret
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methodData = new byte[] { 0x16, 0x2A };
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}
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else {
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tokenToNativeMethod[methodToken] = methodData;
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// ldc.i4 0xDEADCODE / conv.u4 / throw
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methodData = new byte[] { 0x20, 0xDE, 0xC0, 0xAD, 0xDE, 0x6D, 0x7A };
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}
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}
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var dm = new DumpedMethod();
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peImage.ReadMethodTableRowTo(dm, MDToken.ToRID(methodToken));
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dm.code = methodData;
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var codeReader = peImage.Reader;
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codeReader.Position = peImage.RvaToOffset(dm.mdRVA);
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byte[] code;
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var mbHeader = MethodBodyParser.ParseMethodBody(codeReader, out code, out dm.extraSections);
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peImage.UpdateMethodHeaderInfo(dm, mbHeader);
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dumpedMethods.Add(dm);
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}
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}
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return true;
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}
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public static bool IsNewer45Decryption(MethodDef method) {
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if (method == null || method.Body == null)
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return false;
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var instrs = method.Body.Instructions;
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for (int i = 0; i < instrs.Count - 4; i++) {
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var ldci4 = instrs[i];
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if (!ldci4.IsLdcI4() || ldci4.GetLdcI4Value() != 4)
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continue;
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if (instrs[i + 1].OpCode.Code != Code.Mul)
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continue;
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ldci4 = instrs[i + 2];
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if (!ldci4.IsLdcI4() || ldci4.GetLdcI4Value() != 4)
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continue;
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if (instrs[i + 3].OpCode.Code != Code.Ldloca_S && instrs[i + 3].OpCode.Code != Code.Ldloca)
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continue;
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var call = instrs[i + 4];
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if (call.OpCode.Code != Code.Call)
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continue;
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if (!DotNetUtils.IsPinvokeMethod(call.Operand as MethodDef, "kernel32", "VirtualProtect"))
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continue;
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return true;
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}
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return false;
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}
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static void PatchDwords(MyPEImage peImage, IBinaryReader reader, int count) {
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for (int i = 0; i < count; i++) {
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uint rva = reader.ReadUInt32();
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uint data = reader.ReadUInt32();
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peImage.DotNetSafeWrite(rva, BitConverter.GetBytes(data));
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}
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}
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long GetXorKey() {
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var instructions = encryptedResource.Method.Body.Instructions;
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for (int i = 0; i < instructions.Count - 1; i++) {
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if (instructions[i].OpCode.Code != Code.Ldind_I8)
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continue;
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var ldci4 = instructions[i + 1];
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if (ldci4.IsLdcI4())
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return ldci4.GetLdcI4Value();
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if (ldci4.OpCode.Code == Code.Ldc_I8)
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return (long)ldci4.Operand;
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}
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return 0;
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}
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public void Reloaded() {
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foreach (var pair in tokenToNativeMethod) {
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int token = (int)pair.Key;
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var method = module.ResolveToken(token) as MethodDef;
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if (method == null)
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throw new ApplicationException(string.Format("Could not find method {0:X8}", token));
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methodToNativeMethod[method] = pair.Value;
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}
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tokenToNativeMethod = null;
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}
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public void PrepareEncryptNativeMethods(ModuleWriterBase moduleWriter) {
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if (methodToNativeMethod.Count == 0)
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return;
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validNativeMethods = new List<MethodDef>(methodToNativeMethod.Count);
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int len = 12;
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foreach (var kv in methodToNativeMethod) {
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if (kv.Key.DeclaringType == null)
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continue; // Method was removed
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if (kv.Key.DeclaringType.Module != module)
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continue; // method.DeclaringType was removed
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validNativeMethods.Add(kv.Key);
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len += 3 * 4 + kv.Value.Length;
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}
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if (validNativeMethods.Count == 0)
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return;
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len = (len & ~15) + 16;
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encryptedResource.Resource.Data = MemoryImageStream.Create(new byte[len]);
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}
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public void EncryptNativeMethods(ModuleWriterBase moduleWriter) {
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if (validNativeMethods == null || validNativeMethods.Count == 0)
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return;
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Logger.v("Encrypting native methods");
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var stream = new MemoryStream();
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var writer = new BinaryWriter(stream);
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writer.Write((uint)0); // patch count
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writer.Write((uint)0); // mode
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writer.Write(validNativeMethods.Count);
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int index = 0;
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foreach (var method in validNativeMethods) {
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var code = methodToNativeMethod[method];
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var mb = moduleWriter.MetaData.GetMethodBody(method);
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if (mb == null) {
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Logger.e("Could not find method body for method {0} ({1:X8})", method, method.MDToken.Raw);
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continue;
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}
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uint codeRva = (uint)mb.RVA;
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if (mb.IsTiny)
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codeRva++;
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else
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codeRva += (uint)(4 * (mb.Code[1] >> 4));
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Logger.v("Native method {0:X8}, code RVA {1:X8}", new MDToken(Table.Method, moduleWriter.MetaData.GetRid(method)).Raw, codeRva);
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writer.Write(codeRva);
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writer.Write(0x70000000 + index++);
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writer.Write(code.Length);
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writer.Write(code);
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}
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if (index != 0)
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Logger.n("Re-encrypted {0}/{1} native methods", index, totalEncryptedNativeMethods);
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var resourceChunk = moduleWriter.MetaData.GetChunk(encryptedResource.Resource);
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var resourceData = resourceChunk.Data;
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var encrypted = stream.ToArray();
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XorEncrypt(encrypted);
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encrypted = encryptedResource.Encrypt(encrypted);
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if (encrypted.Length != resourceData.Length)
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Logger.e("Encrypted native methods array is not same size as original array");
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Array.Copy(encrypted, resourceData, resourceData.Length);
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}
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enum CompileMethodType {
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Unknown,
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V1, // <= DNR 4.5.0.0 (2012-11-06 <= endDate < 2013-01-31)
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V2, // >= DNR 4.5.0.0 (2012-11-06 < startDate <= 2013-01-31)
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}
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public static MethodDef FindDnrCompileMethod(TypeDef type) {
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foreach (var method in type.Methods) {
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if (!method.IsStatic || method.Body == null)
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continue;
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var sig = method.MethodSig;
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if (sig == null || sig.Params.Count != 6)
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continue;
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if (GetCompileMethodType(method) == CompileMethodType.Unknown)
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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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static CompileMethodType GetCompileMethodType(MethodDef method) {
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if (DotNetUtils.IsMethod(method, "System.UInt32", "(System.UInt64&,System.IntPtr,System.IntPtr,System.UInt32,System.IntPtr&,System.UInt32&)"))
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return CompileMethodType.V1;
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if (DotNetUtils.IsMethod(method, "System.UInt32", "(System.IntPtr,System.IntPtr,System.IntPtr,System.UInt32,System.IntPtr,System.UInt32&)"))
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return CompileMethodType.V2;
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return CompileMethodType.Unknown;
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}
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}
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}
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