/*
Copyright (C) 2011-2012 de4dot@gmail.com
This file is part of de4dot.
de4dot is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
de4dot is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with de4dot. If not, see .
*/
using System.Collections.Generic;
using dot10.DotNet;
using dot10.DotNet.Emit;
namespace de4dot.blocks.cflow {
public abstract class MethodCallInlinerBase : IBlocksDeobfuscator {
// We can't catch all infinite loops, so inline methods at most this many times
const int MAX_ITERATIONS = 10;
protected Blocks blocks;
protected Block block;
int iteration;
AccessChecker accessChecker;
public bool ExecuteOnNoChange { get; set; }
public void deobfuscateBegin(Blocks blocks) {
this.blocks = blocks;
iteration = 0;
}
public bool deobfuscate(List allBlocks) {
if (iteration++ >= MAX_ITERATIONS)
return false;
bool changed = false;
foreach (var block in allBlocks) {
this.block = block;
changed |= deobfuscateInternal();
}
return changed;
}
protected abstract bool deobfuscateInternal();
protected class InstructionPatcher {
readonly int patchIndex;
public readonly int afterIndex;
public readonly Instruction lastInstr;
readonly Instr clonedInstr;
public InstructionPatcher(int patchIndex, int afterIndex, Instruction lastInstr) {
this.patchIndex = patchIndex;
this.afterIndex = afterIndex;
this.lastInstr = lastInstr;
this.clonedInstr = new Instr(lastInstr.Clone());
}
public void patch(Block block) {
block.Instructions[patchIndex] = clonedInstr;
}
}
protected bool inlineLoadMethod(int patchIndex, MethodDef methodToInline, Instruction loadInstr, int instrIndex) {
if (!isReturn(methodToInline, instrIndex))
return false;
int methodArgsCount = DotNetUtils.getArgsCount(methodToInline);
for (int i = 0; i < methodArgsCount; i++)
block.insert(patchIndex++, Instruction.Create(OpCodes.Pop));
block.Instructions[patchIndex] = new Instr(loadInstr.Clone());
return true;
}
protected bool inlineOtherMethod(int patchIndex, MethodDef methodToInline, Instruction instr, int instrIndex) {
return inlineOtherMethod(patchIndex, methodToInline, instr, instrIndex, 0);
}
protected bool inlineOtherMethod(int patchIndex, MethodDef methodToInline, Instruction instr, int instrIndex, int popLastArgs) {
return patchMethod(methodToInline, tryInlineOtherMethod(patchIndex, methodToInline, instr, instrIndex, popLastArgs));
}
protected bool patchMethod(MethodDef methodToInline, InstructionPatcher patcher) {
if (patcher == null)
return false;
if (!isReturn(methodToInline, patcher.afterIndex))
return false;
patcher.patch(block);
return true;
}
protected InstructionPatcher tryInlineOtherMethod(int patchIndex, MethodDef methodToInline, Instruction instr, int instrIndex) {
return tryInlineOtherMethod(patchIndex, methodToInline, instr, instrIndex, 0);
}
protected InstructionPatcher tryInlineOtherMethod(int patchIndex, MethodDef methodToInline, Instruction instr, int instrIndex, int popLastArgs) {
int loadIndex = 0;
int methodArgsCount = DotNetUtils.getArgsCount(methodToInline);
bool foundLdarga = false;
while (instr != null && loadIndex < methodArgsCount) {
bool isLdarg = true;
switch (instr.OpCode.Code) {
case Code.Ldarg:
case Code.Ldarg_S:
case Code.Ldarg_0:
case Code.Ldarg_1:
case Code.Ldarg_2:
case Code.Ldarg_3:
break;
case Code.Ldarga:
case Code.Ldarga_S:
foundLdarga = true;
break;
default:
isLdarg = false;
break;
}
if (!isLdarg)
break;
if (instr.GetParameterIndex() != loadIndex)
return null;
loadIndex++;
instr = DotNetUtils.getInstruction(methodToInline.Body.Instructions, ref instrIndex);
}
if (instr == null || loadIndex != methodArgsCount - popLastArgs)
return null;
if (instr.OpCode.Code == Code.Call || instr.OpCode.Code == Code.Callvirt) {
if (foundLdarga)
return null;
var callInstr = instr;
var calledMethod = callInstr.Operand as IMethod;
if (calledMethod == null)
return null;
if (!isCompatibleType(-1, calledMethod.MethodSig.RetType, methodToInline.MethodSig.RetType))
return null;
if (!checkSameMethods(calledMethod, methodToInline, popLastArgs))
return null;
if (!hasAccessTo(instr.Operand))
return null;
return new InstructionPatcher(patchIndex, instrIndex, callInstr);
}
else if (instr.OpCode.Code == Code.Newobj) {
if (foundLdarga)
return null;
var newobjInstr = instr;
var ctor = newobjInstr.Operand as IMethod;
if (ctor == null)
return null;
if (!isCompatibleType(-1, ctor.DeclaringType, methodToInline.MethodSig.RetType))
return null;
var methodArgs = methodToInline.Parameters;
var calledMethodArgs = DotNetUtils.getArgs(ctor);
if (methodArgs.Count + 1 - popLastArgs != calledMethodArgs.Count)
return null;
for (int i = 1; i < calledMethodArgs.Count; i++) {
if (!isCompatibleType(i, calledMethodArgs[i], methodArgs[i - 1].Type))
return null;
}
if (!hasAccessTo(instr.Operand))
return null;
return new InstructionPatcher(patchIndex, instrIndex, newobjInstr);
}
else if (instr.OpCode.Code == Code.Ldfld || instr.OpCode.Code == Code.Ldflda ||
instr.OpCode.Code == Code.Ldftn || instr.OpCode.Code == Code.Ldvirtftn) {
var ldInstr = instr;
if (methodArgsCount != 1)
return null;
if (!hasAccessTo(instr.Operand))
return null;
return new InstructionPatcher(patchIndex, instrIndex, ldInstr);
}
return null;
}
bool hasAccessTo(object operand) {
if (operand == null)
return false;
accessChecker.UserType = blocks.Method.DeclaringType;
return accessChecker.CanAccess(operand) ?? getDefaultAccessResult();
}
protected virtual bool getDefaultAccessResult() {
return true;
}
protected virtual bool isReturn(MethodDef methodToInline, int instrIndex) {
var instr = DotNetUtils.getInstruction(methodToInline.Body.Instructions, ref instrIndex);
return instr != null && instr.OpCode.Code == Code.Ret;
}
protected bool checkSameMethods(IMethod method, MethodDef methodToInline) {
return checkSameMethods(method, methodToInline, 0);
}
protected bool checkSameMethods(IMethod method, MethodDef methodToInline, int ignoreLastMethodToInlineArgs) {
var methodToInlineArgs = methodToInline.Parameters;
var methodArgs = DotNetUtils.getArgs(method);
bool hasImplicitThis = method.MethodSig.ImplicitThis;
if (methodToInlineArgs.Count - ignoreLastMethodToInlineArgs != methodArgs.Count)
return false;
for (int i = 0; i < methodArgs.Count; i++) {
var methodArg = methodArgs[i];
var methodToInlineArg = methodToInlineArgs[i].Type;
if (!isCompatibleType(i, methodArg, methodToInlineArg)) {
if (i != 0 || !hasImplicitThis)
return false;
if (!isCompatibleValueThisPtr(methodArg, methodToInlineArg))
return false;
}
}
return true;
}
protected virtual bool isCompatibleType(int paramIndex, IType origType, IType newType) {
return new SigComparer().Equals(origType, newType);
}
static bool isCompatibleValueThisPtr(IType origType, IType newType) {
var newByRef = newType as ByRefSig;
if (newByRef == null)
return false;
if (!isValueType(newByRef.Next) || !isValueType(origType))
return false;
return new SigComparer().Equals(origType, newByRef.Next);
}
protected static bool isValueType(IType type) {
if (type == null)
return false;
var ts = type as TypeSig;
if (ts == null)
return type.IsValueType;
return ts.IsValueType && ts.ElementType != ElementType.Void;
}
}
}