587 lines
17 KiB
C#
587 lines
17 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.IO;
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using System.Text;
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using dnlib.IO;
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using dnlib.DotNet;
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using dnlib.DotNet.Emit;
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using de4dot.blocks;
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using de4dot.blocks.cflow;
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namespace de4dot.code.deobfuscators.Babel_NET {
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class StringDecrypter {
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ModuleDefMD module;
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ResourceDecrypter resourceDecrypter;
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ISimpleDeobfuscator simpleDeobfuscator;
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TypeDef decrypterType;
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EmbeddedResource encryptedResource;
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IDecrypterInfo decrypterInfo;
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interface IDecrypterInfo {
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MethodDef Decrypter { get; }
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bool NeedsResource { get; }
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void Initialize(ModuleDefMD module, EmbeddedResource resource);
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string Decrypt(object[] args);
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}
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// Babel .NET 2.x
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class DecrypterInfoV1 : IDecrypterInfo {
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public MethodDef Decrypter { get; set; }
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public bool NeedsResource {
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get { return false; }
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}
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public void Initialize(ModuleDefMD module, EmbeddedResource resource) {
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}
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public string Decrypt(object[] args) {
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return Decrypt((string)args[0], (int)args[1]);
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}
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string Decrypt(string s, int k) {
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var sb = new StringBuilder(s.Length);
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foreach (var c in s)
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sb.Append((char)(c ^ k));
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return sb.ToString();
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}
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}
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class DecrypterInfoV2 : IDecrypterInfo {
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byte[] key;
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public MethodDef Decrypter { get; set; }
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public bool NeedsResource {
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get { return true; }
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}
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public void Initialize(ModuleDefMD module, EmbeddedResource resource) {
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key = resource.Data.ReadAllBytes();
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if (key.Length != 0x100)
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throw new ApplicationException(string.Format("Unknown key length: {0}", key.Length));
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}
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public string Decrypt(object[] args) {
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return Decrypt((string)args[0], (int)args[1]);
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}
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string Decrypt(string s, int k) {
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var sb = new StringBuilder(s.Length);
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byte b = key[(byte)k];
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foreach (var c in s)
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sb.Append((char)(c ^ (b | k)));
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return sb.ToString();
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}
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}
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class DecrypterInfoV3 : IDecrypterInfo {
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Dictionary<int, string> offsetToString = new Dictionary<int, string>();
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ResourceDecrypter resourceDecrypter;
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InstructionEmulator emulator = new InstructionEmulator();
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public IList<Instruction> OffsetCalcInstructions { get; set; }
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public MethodDef Decrypter { get; set; }
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public bool NeedsResource {
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get { return true; }
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}
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public DecrypterInfoV3(ResourceDecrypter resourceDecrypter) {
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this.resourceDecrypter = resourceDecrypter;
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}
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public void Initialize(ModuleDefMD module, EmbeddedResource resource) {
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var decrypted = resourceDecrypter.Decrypt(resource.Data.ReadAllBytes());
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var reader = new BinaryReader(new MemoryStream(decrypted));
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while (reader.BaseStream.Position < reader.BaseStream.Length)
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offsetToString[GetOffset((int)reader.BaseStream.Position)] = reader.ReadString();
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}
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MethodDef dummyMethod;
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int GetOffset(int offset) {
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if (OffsetCalcInstructions == null || OffsetCalcInstructions.Count == 0)
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return offset;
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if (dummyMethod == null) {
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dummyMethod = new MethodDefUser();
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dummyMethod.Body = new CilBody();
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}
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emulator.Initialize(dummyMethod);
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emulator.Push(new Int32Value(offset));
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foreach (var instr in OffsetCalcInstructions)
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emulator.Emulate(instr);
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return ((Int32Value)emulator.Pop()).Value;
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}
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public string Decrypt(object[] args) {
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return Decrypt((int)args[0]);
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}
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string Decrypt(int offset) {
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return offsetToString[offset];
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}
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}
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public bool Detected {
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get { return decrypterType != null; }
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}
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public TypeDef Type {
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get { return decrypterType; }
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}
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public MethodDef DecryptMethod {
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get { return decrypterInfo == null ? null : decrypterInfo.Decrypter; }
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}
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public EmbeddedResource Resource {
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get { return encryptedResource; }
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}
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public StringDecrypter(ModuleDefMD module, ResourceDecrypter resourceDecrypter) {
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this.module = module;
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this.resourceDecrypter = resourceDecrypter;
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}
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public void Find(ISimpleDeobfuscator simpleDeobfuscator) {
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this.simpleDeobfuscator = simpleDeobfuscator;
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foreach (var type in module.Types) {
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var info = CheckDecrypterType(type);
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if (info == null)
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continue;
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decrypterType = type;
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decrypterInfo = info;
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return;
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}
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}
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IDecrypterInfo CheckDecrypterType(TypeDef type) {
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if (type.HasEvents)
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return null;
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if (type.NestedTypes.Count > 2)
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return null;
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if (type.Fields.Count > 1)
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return null;
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foreach (var nested in type.NestedTypes) {
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var info = CheckNested(type, nested);
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if (info != null)
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return info;
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}
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return CheckDecrypterTypeBabel2x(type);
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}
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IDecrypterInfo CheckDecrypterTypeBabel2x(TypeDef type) {
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if (type.HasEvents || type.HasProperties || type.HasNestedTypes)
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return null;
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if (type.HasFields || type.Methods.Count != 1)
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return null;
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var decrypter = type.Methods[0];
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if (!CheckDecryptMethodBabel2x(decrypter))
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return null;
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return new DecrypterInfoV1 { Decrypter = decrypter };
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}
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bool CheckDecryptMethodBabel2x(MethodDef method) {
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if (!method.IsStatic || !method.IsPublic)
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return false;
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if (method.Body == null)
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return false;
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if (method.Name == ".cctor")
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return false;
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if (!DotNetUtils.IsMethod(method, "System.String", "(System.String,System.Int32)"))
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return false;
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int stringLength = 0, stringToCharArray = 0, stringCtor = 0;
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foreach (var instr in method.Body.Instructions) {
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var calledMethod = instr.Operand as IMethod;
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if (calledMethod == null)
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continue;
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switch (instr.OpCode.Code) {
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case Code.Call:
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case Code.Callvirt:
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if (calledMethod.FullName == "System.Int32 System.String::get_Length()")
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stringLength++;
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else if (calledMethod.FullName == "System.Char[] System.String::ToCharArray()")
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stringToCharArray++;
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else
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return false;
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break;
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case Code.Newobj:
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if (calledMethod.FullName == "System.Void System.String::.ctor(System.Char[])")
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stringCtor++;
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else
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return false;
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break;
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default:
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continue;
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}
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}
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return stringLength == 1 && stringToCharArray == 1 && stringCtor == 1;
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}
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IDecrypterInfo CheckNested(TypeDef type, TypeDef nested) {
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if (nested.HasProperties || nested.HasEvents)
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return null;
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if (nested.FindMethod(".ctor") == null)
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return null;
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if (nested.Fields.Count == 1 || nested.Fields.Count == 3) {
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// 4.0+
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if (!HasFieldType(nested.Fields, nested))
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return null;
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var decrypterBuilderMethod = DotNetUtils.GetMethod(nested, "System.Reflection.Emit.MethodBuilder", "(System.Reflection.Emit.TypeBuilder)");
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if (decrypterBuilderMethod == null)
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return null;
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resourceDecrypter.DecryptMethod = ResourceDecrypter.FindDecrypterMethod(nested.FindMethod(".ctor"));
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var nestedDecrypter = DotNetUtils.GetMethod(nested, "System.String", "(System.Int32)");
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if (nestedDecrypter == null || nestedDecrypter.IsStatic)
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return null;
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var decrypter = DotNetUtils.GetMethod(type, "System.String", "(System.Int32)");
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if (decrypter == null || !decrypter.IsStatic)
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return null;
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simpleDeobfuscator.Deobfuscate(decrypterBuilderMethod);
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return new DecrypterInfoV3(resourceDecrypter) {
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Decrypter = decrypter,
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OffsetCalcInstructions = GetOffsetCalcInstructions(decrypterBuilderMethod),
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};
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}
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else if (nested.Fields.Count == 2) {
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// 3.0 - 3.5
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if (CheckFields(nested, "System.Collections.Hashtable", nested)) {
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// 3.0 - 3.5
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var nestedDecrypter = DotNetUtils.GetMethod(nested, "System.String", "(System.Int32)");
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if (nestedDecrypter == null || nestedDecrypter.IsStatic)
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return null;
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var decrypter = DotNetUtils.GetMethod(type, "System.String", "(System.Int32)");
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if (decrypter == null || !decrypter.IsStatic)
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return null;
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resourceDecrypter.DecryptMethod = ResourceDecrypter.FindDecrypterMethod(nested.FindMethod(".ctor"));
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return new DecrypterInfoV3(resourceDecrypter) { Decrypter = decrypter };
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}
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else if (CheckFields(nested, "System.Byte[]", nested)) {
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// 3.0
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var nestedDecrypter = DotNetUtils.GetMethod(nested, "System.String", "(System.String,System.Int32)");
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if (nestedDecrypter == null || nestedDecrypter.IsStatic)
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return null;
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var decrypter = DotNetUtils.GetMethod(type, "System.String", "(System.String,System.Int32)");
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if (decrypter == null || !decrypter.IsStatic)
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return null;
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return new DecrypterInfoV2 { Decrypter = decrypter };
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}
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else
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return null;
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}
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return null;
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}
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class ReflectionToDNLibMethodCreator {
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MethodDef method;
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List<Instruction> instructions = new List<Instruction>();
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InstructionEmulator emulator;
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int index;
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class UserValue : UnknownValue {
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public readonly object obj;
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public UserValue(object obj) {
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this.obj = obj;
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}
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public override string ToString() {
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if (obj == null)
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return "<null>";
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return obj.ToString();
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}
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}
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public List<Instruction> Instructions {
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get { return instructions; }
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}
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public ReflectionToDNLibMethodCreator(MethodDef method) {
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this.method = method;
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this.emulator = new InstructionEmulator(method);
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}
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public bool Create() {
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int arrayIndex;
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Value array;
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object value;
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while (true) {
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var instr = method.Body.Instructions[index];
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switch (instr.OpCode.Code) {
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case Code.Ret:
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return true;
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case Code.Newarr:
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var arrayType = (ITypeDefOrRef)instr.Operand;
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int arrayCount = ((Int32Value)emulator.Pop()).Value;
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if (arrayType.FullName == "System.Char")
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emulator.Push(new UserValue(new char[arrayCount]));
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else
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emulator.Push(new UnknownValue());
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break;
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case Code.Call:
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case Code.Callvirt:
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if (!DoCall(instr))
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return false;
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break;
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case Code.Ldelem_U1:
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arrayIndex = ((Int32Value)emulator.Pop()).Value;
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array = (Value)emulator.Pop();
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if (array is UserValue)
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emulator.Push(new Int32Value(((byte[])((UserValue)array).obj)[arrayIndex]));
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else
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emulator.Push(Int32Value.CreateUnknownUInt8());
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break;
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case Code.Stelem_I1:
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value = emulator.Pop();
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arrayIndex = ((Int32Value)emulator.Pop()).Value;
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array = (Value)emulator.Pop();
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if (array is UserValue)
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((byte[])((UserValue)array).obj)[arrayIndex] = (byte)((Int32Value)value).Value;
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break;
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case Code.Stelem_I2:
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value = emulator.Pop();
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arrayIndex = ((Int32Value)emulator.Pop()).Value;
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array = (Value)emulator.Pop();
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if (array is UserValue)
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((char[])((UserValue)array).obj)[arrayIndex] = (char)((Int32Value)value).Value;
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break;
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case Code.Ldelem_Ref:
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arrayIndex = ((Int32Value)emulator.Pop()).Value;
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array = (Value)emulator.Pop();
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var userValue = array as UserValue;
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if (userValue != null && userValue.obj is string[])
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emulator.Push(new StringValue(((string[])userValue.obj)[arrayIndex]));
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else
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emulator.Push(new UnknownValue());
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break;
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case Code.Ldsfld:
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emulator.Push(new UserValue((IField)instr.Operand));
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break;
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default:
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emulator.Emulate(instr);
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break;
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}
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index++;
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}
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}
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bool DoCall(Instruction instr) {
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var calledMethod = (IMethod)instr.Operand;
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var sig = calledMethod.MethodSig;
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var fn = calledMethod.FullName;
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if (fn == "System.Byte[] System.Convert::FromBase64String(System.String)") {
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emulator.Push(new UserValue(Convert.FromBase64String(((StringValue)emulator.Pop()).value)));
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return true;
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}
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else if (fn == "System.String System.Text.Encoding::GetString(System.Byte[])") {
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emulator.Push(new StringValue(Encoding.UTF8.GetString((byte[])((UserValue)emulator.Pop()).obj)));
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return true;
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}
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else if (fn == "System.Int32 System.Int32::Parse(System.String)") {
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emulator.Push(new Int32Value(int.Parse(((StringValue)emulator.Pop()).value)));
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return true;
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}
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else if (fn == "System.String[] System.String::Split(System.Char[])") {
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var ary = (char[])((UserValue)emulator.Pop()).obj;
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var s = ((StringValue)emulator.Pop()).value;
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emulator.Push(new UserValue(s.Split(ary)));
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return true;
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}
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else if (sig != null && sig.HasThis && calledMethod.DeclaringType.FullName == "System.Reflection.Emit.ILGenerator" && calledMethod.Name == "Emit") {
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Value operand = null;
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if (calledMethod.MethodSig.GetParamCount() == 2)
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operand = emulator.Pop();
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var opcode = ReflectionToOpCode((IField)((UserValue)emulator.Pop()).obj);
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emulator.Pop(); // the this ptr
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AddInstruction(new Instruction {
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OpCode = opcode,
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Operand = CreateDNLibOperand(opcode, operand),
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});
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return true;
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}
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else {
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emulator.Emulate(instr);
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return true;
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}
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}
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object CreateDNLibOperand(OpCode opcode, Value op) {
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if (op is Int32Value)
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return ((Int32Value)op).Value;
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if (op is StringValue)
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return ((StringValue)op).value;
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return null;
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}
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void AddInstruction(Instruction instr) {
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instructions.Add(instr);
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}
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static OpCode ReflectionToOpCode(IField reflectionField) {
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var field = typeof(OpCodes).GetField(reflectionField.Name.String);
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if (field == null || field.FieldType != typeof(OpCode))
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return null;
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return (OpCode)field.GetValue(null);
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}
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}
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static List<Instruction> GetOffsetCalcInstructions(MethodDef method) {
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var creator = new ReflectionToDNLibMethodCreator(method);
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creator.Create();
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var instrs = creator.Instructions;
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int index = 0;
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index = FindInstruction(instrs, index, OpCodes.Conv_I4);
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if (index < 0)
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return null;
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int startInstr = ++index;
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index = FindInstruction(instrs, index, OpCodes.Box);
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if (index < 0)
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return null;
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int endInstr = index - 1;
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var transformInstructions = new List<Instruction>();
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for (int i = startInstr; i <= endInstr; i++)
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transformInstructions.Add(instrs[i]);
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return transformInstructions;
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}
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static int FindInstruction(IList<Instruction> instrs, int index, OpCode opcode) {
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if (index < 0)
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return -1;
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for (int i = index; i < instrs.Count; i++) {
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if (instrs[i].OpCode == opcode)
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return i;
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}
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return -1;
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}
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static bool HasFieldType(IEnumerable<FieldDef> fields, TypeDef fieldType) {
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foreach (var field in fields) {
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if (new SigComparer().Equals(field.FieldSig.GetFieldType(), fieldType))
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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 int GetOffsetMagic(MethodDef method) {
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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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int index = i;
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var ldsfld1 = instrs[index++];
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if (ldsfld1.OpCode.Code != Code.Ldsfld)
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continue;
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var ldci4 = instrs[index++];
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if (!ldci4.IsLdcI4())
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continue;
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var callvirt = instrs[index++];
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|
if (callvirt.OpCode.Code != Code.Callvirt)
|
|
continue;
|
|
var calledMethod = callvirt.Operand as IMethod;
|
|
if (calledMethod == null)
|
|
continue;
|
|
if (calledMethod.FullName != "System.Void System.Reflection.Emit.ILGenerator::Emit(System.Reflection.Emit.OpCode,System.Int32)")
|
|
continue;
|
|
|
|
if (!instrs[index++].IsLdloc())
|
|
continue;
|
|
|
|
var ldsfld2 = instrs[index++];
|
|
if (ldsfld2.OpCode.Code != Code.Ldsfld)
|
|
continue;
|
|
var field = ldsfld2.Operand as IField;
|
|
if (field == null)
|
|
continue;
|
|
if (field.FullName != "System.Reflection.Emit.OpCode System.Reflection.Emit.OpCodes::Xor")
|
|
continue;
|
|
|
|
// Here if Babel.NET 5.5
|
|
return ldci4.GetLdcI4Value();
|
|
}
|
|
|
|
// Here if Babel.NET <= 5.0
|
|
return 0;
|
|
}
|
|
|
|
bool CheckFields(TypeDef type, string fieldType1, TypeDef fieldType2) {
|
|
if (type.Fields.Count != 2)
|
|
return false;
|
|
if (type.Fields[0].FieldSig.GetFieldType().GetFullName() != fieldType1 &&
|
|
type.Fields[1].FieldSig.GetFieldType().GetFullName() != fieldType1)
|
|
return false;
|
|
if (!new SigComparer().Equals(type.Fields[0].FieldSig.GetFieldType(), fieldType2) &&
|
|
!new SigComparer().Equals(type.Fields[1].FieldSig.GetFieldType(), fieldType2))
|
|
return false;
|
|
return true;
|
|
}
|
|
|
|
public void Initialize() {
|
|
if (decrypterType == null)
|
|
return;
|
|
if (encryptedResource != null)
|
|
return;
|
|
|
|
if (decrypterInfo.NeedsResource) {
|
|
encryptedResource = BabelUtils.FindEmbeddedResource(module, decrypterType);
|
|
if (encryptedResource == null)
|
|
return;
|
|
}
|
|
|
|
decrypterInfo.Initialize(module, encryptedResource);
|
|
}
|
|
|
|
public string Decrypt(object[] args) {
|
|
return decrypterInfo.Decrypt(args);
|
|
}
|
|
}
|
|
}
|