106 lines
3.0 KiB
C#
106 lines
3.0 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.DotNet;
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using dnlib.DotNet.Emit;
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using de4dot.blocks;
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namespace de4dot.blocks.cflow {
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// Very simple constants folder which is all that's needed at the moment
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class ConstantsFolder : BlockDeobfuscator {
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InstructionEmulator instructionEmulator = new InstructionEmulator();
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IList<Parameter> args;
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protected override void Initialize(List<Block> allBlocks) {
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base.Initialize(allBlocks);
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args = blocks.Method.Parameters;
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}
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protected override bool Deobfuscate(Block block) {
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bool modified = false;
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instructionEmulator.Initialize(blocks);
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var instrs = block.Instructions;
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for (int i = 0; i < instrs.Count; i++) {
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var instr = instrs[i];
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switch (instr.OpCode.Code) {
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case Code.Ldarg:
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case Code.Ldarg_0:
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case Code.Ldarg_1:
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case Code.Ldarg_2:
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case Code.Ldarg_3:
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case Code.Ldarg_S:
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modified |= FixLoadInstruction(block, i, instructionEmulator.GetArg(instr.Instruction.GetParameter(args)));
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break;
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case Code.Ldloc:
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case Code.Ldloc_0:
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case Code.Ldloc_1:
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case Code.Ldloc_2:
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case Code.Ldloc_3:
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case Code.Ldloc_S:
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modified |= FixLoadInstruction(block, i, instructionEmulator.GetLocal(instr.Instruction.GetLocal(blocks.Locals)));
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break;
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case Code.Ldarga:
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case Code.Ldarga_S:
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instructionEmulator.MakeArgUnknown((Parameter)instr.Operand);
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break;
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case Code.Ldloca:
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case Code.Ldloca_S:
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instructionEmulator.MakeLocalUnknown((Local)instr.Operand);
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break;
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}
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try {
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instructionEmulator.Emulate(instr.Instruction);
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}
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catch (NullReferenceException) {
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// Here if eg. invalid metadata token in a call instruction (operand is null)
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break;
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}
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}
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return modified;
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}
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bool FixLoadInstruction(Block block, int index, Value value) {
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if (value.IsInt32()) {
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var intValue = (Int32Value)value;
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if (!intValue.AllBitsValid())
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return false;
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block.Instructions[index] = new Instr(Instruction.CreateLdcI4(intValue.Value));
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return true;
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}
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else if (value.IsInt64()) {
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var intValue = (Int64Value)value;
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if (!intValue.AllBitsValid())
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return false;
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block.Instructions[index] = new Instr(OpCodes.Ldc_I8.ToInstruction(intValue.Value));
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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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