80 lines
2.5 KiB
C#
80 lines
2.5 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 dnlib.DotNet.Emit;
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namespace de4dot.blocks.cflow {
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class BlockCflowDeobfuscator : BlockDeobfuscator, IBranchHandler {
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Block block;
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InstructionEmulator instructionEmulator;
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BranchEmulator branchEmulator;
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public BlockCflowDeobfuscator() {
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instructionEmulator = new InstructionEmulator();
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branchEmulator = new BranchEmulator(instructionEmulator, this);
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}
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protected override bool Deobfuscate(Block block) {
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this.block = block;
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if (!block.LastInstr.IsConditionalBranch() && block.LastInstr.OpCode.Code != Code.Switch)
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return false;
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instructionEmulator.Initialize(blocks, allBlocks[0] == block);
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var instructions = block.Instructions;
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if (instructions.Count == 0)
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return false;
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try {
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for (int i = 0; i < instructions.Count - 1; i++) {
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var instr = instructions[i].Instruction;
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instructionEmulator.Emulate(instr);
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}
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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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return false;
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}
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return branchEmulator.Emulate(block.LastInstr.Instruction);
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}
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void PopPushedArgs(int stackArgs) {
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// Pop the arguments to the bcc instruction. The dead code remover will get rid of the
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// pop and any pushed arguments. Insert the pops just before the bcc instr.
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for (int i = 0; i < stackArgs; i++)
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block.Insert(block.Instructions.Count - 1, OpCodes.Pop.ToInstruction());
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}
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void IBranchHandler.HandleNormal(int stackArgs, bool isTaken) {
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PopPushedArgs(stackArgs);
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block.ReplaceBccWithBranch(isTaken);
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}
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bool IBranchHandler.HandleSwitch(Int32Value switchIndex) {
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var target = CflowUtils.GetSwitchTarget(block.Targets, block.FallThrough, switchIndex);
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if (target == null)
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return false;
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PopPushedArgs(1);
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block.ReplaceSwitchWithBranch(target);
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return true;
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}
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}
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}
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