206 lines
6.0 KiB
C#
206 lines
6.0 KiB
C#
/*
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Copyright (C) 2011-2013 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 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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namespace de4dot.code.deobfuscators.CryptoObfuscator {
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class MethodsDecrypter {
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ModuleDefMD module;
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TypeDef decrypterType;
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MethodDef decryptMethod;
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MethodDef decrypterCctor;
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EmbeddedResource resource;
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List<TypeDef> delegateTypes = new List<TypeDef>();
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public TypeDef Type {
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get { return decrypterType; }
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}
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public IEnumerable<TypeDef> DelegateTypes {
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get { return delegateTypes; }
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}
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public EmbeddedResource Resource {
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get { return resource; }
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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 MethodsDecrypter(ModuleDefMD module) {
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this.module = module;
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}
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public void Find() {
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foreach (var type in module.Types) {
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if (Check(type))
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break;
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}
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}
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static readonly string[] requiredFields = new string[] {
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"System.Byte[]",
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"System.Collections.Generic.Dictionary`2<System.Int32,System.Int32>",
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"System.ModuleHandle",
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};
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bool Check(TypeDef type) {
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if (type.NestedTypes.Count != 1)
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return false;
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if (type.Fields.Count != 3)
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return false;
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if (!new FieldTypes(type).All(requiredFields))
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return false;
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var cctor = type.FindStaticConstructor();
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if (cctor == null)
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return false;
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var decryptMethodTmp = FindDecryptMethod(type);
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if (decryptMethodTmp == null)
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return false;
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decryptMethod = decryptMethodTmp;
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decrypterCctor = cctor;
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decrypterType = type;
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return true;
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}
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static readonly string[] requiredLocals = new string[] {
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"System.Delegate",
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"System.ModuleHandle",
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"System.Reflection.Emit.DynamicILInfo",
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"System.Reflection.Emit.DynamicMethod",
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"System.Reflection.FieldInfo",
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"System.Reflection.FieldInfo[]",
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"System.Reflection.MethodBase",
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"System.Reflection.MethodBody",
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"System.Type",
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"System.Type[]",
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};
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static MethodDef FindDecryptMethod(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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if (!new LocalTypes(method).All(requiredLocals))
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continue;
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if (!DotNetUtils.IsMethod(method, "System.Void", "(System.Int32,System.Int32,System.Int32)"))
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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 Decrypt(ResourceDecrypter resourceDecrypter) {
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if (decryptMethod == null)
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return;
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resource = CoUtils.GetResource(module, decrypterCctor);
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if (resource == null)
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return;
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var decrypted = resourceDecrypter.Decrypt(resource.GetResourceStream());
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var reader = MemoryImageStream.Create(decrypted);
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int numEncrypted = reader.ReadInt32();
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Logger.v("Restoring {0} encrypted methods", numEncrypted);
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Logger.Instance.Indent();
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for (int i = 0; i < numEncrypted; i++) {
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int delegateTypeToken = reader.ReadInt32();
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uint codeOffset = reader.ReadUInt32();
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var origOffset = reader.Position;
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reader.Position = codeOffset;
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Decrypt(reader, delegateTypeToken);
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reader.Position = origOffset;
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}
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Logger.Instance.DeIndent();
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}
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void Decrypt(IBinaryReader reader, int delegateTypeToken) {
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var delegateType = module.ResolveToken(delegateTypeToken) as TypeDef;
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if (delegateType == null)
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throw new ApplicationException("Couldn't find delegate type");
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int delToken, encMethToken, encDeclToken;
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if (!GetTokens(delegateType, out delToken, out encMethToken, out encDeclToken))
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throw new ApplicationException("Could not find encrypted method tokens");
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if (delToken != delegateTypeToken)
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throw new ApplicationException("Invalid delegate type token");
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var encType = module.ResolveToken(encDeclToken) as ITypeDefOrRef;
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if (encType == null)
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throw new ApplicationException("Invalid declaring type token");
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var encMethod = module.ResolveToken(encMethToken) as MethodDef;
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if (encMethod == null)
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throw new ApplicationException("Invalid encrypted method token");
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var bodyReader = new MethodBodyReader(module, reader);
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bodyReader.Read(encMethod);
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bodyReader.RestoreMethod(encMethod);
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Logger.v("Restored method {0} ({1:X8}). Instrs:{2}, Locals:{3}, Exceptions:{4}",
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Utils.RemoveNewlines(encMethod.FullName),
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encMethod.MDToken.ToInt32(),
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encMethod.Body.Instructions.Count,
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encMethod.Body.Variables.Count,
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encMethod.Body.ExceptionHandlers.Count);
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delegateTypes.Add(delegateType);
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}
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bool GetTokens(TypeDef delegateType, out int delegateToken, out int encMethodToken, out int encDeclaringTypeToken) {
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delegateToken = 0;
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encMethodToken = 0;
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encDeclaringTypeToken = 0;
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var cctor = delegateType.FindStaticConstructor();
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if (cctor == null)
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return false;
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var instrs = cctor.Body.Instructions;
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for (int i = 0; i < instrs.Count - 3; i++) {
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var ldci4_1 = instrs[i];
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if (!ldci4_1.IsLdcI4())
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continue;
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var ldci4_2 = instrs[i + 1];
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if (!ldci4_2.IsLdcI4())
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continue;
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var ldci4_3 = instrs[i + 2];
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if (!ldci4_3.IsLdcI4())
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continue;
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var call = instrs[i + 3];
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if (call.OpCode.Code != Code.Call)
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continue;
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var calledMethod = call.Operand as MethodDef;
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if (calledMethod == null)
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continue;
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if (calledMethod != decryptMethod)
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continue;
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delegateToken = ldci4_1.GetLdcI4Value();
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encMethodToken = ldci4_2.GetLdcI4Value();
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encDeclaringTypeToken = ldci4_3.GetLdcI4Value();
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return true;
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}
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return false;
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}
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}
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}
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