105 lines
2.9 KiB
C#
105 lines
2.9 KiB
C#
/*
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Copyright (C) 2011 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.Collections.Generic;
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using Mono.Cecil.Cil;
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using de4dot.blocks;
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namespace de4dot.blocks {
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abstract class CondBranchDeobfuscator {
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ScopeBlock scopeBlock;
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IEnumerable<Block> blocks;
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public CondBranchDeobfuscator(ScopeBlock scopeBlock, IEnumerable<Block> blocks) {
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this.scopeBlock = scopeBlock;
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this.blocks = blocks;
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}
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protected abstract bool isTaken(int value);
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public bool deobfuscate() {
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bool removed = false;
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int value = 0;
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var deadBlocks = new List<Block>();
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foreach (var block in blocks) {
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if (block.Instructions.Count > 1) {
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if (getLdcValue(block.Instructions, block.Instructions.Count - 2, ref value)) {
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removed = true;
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if (isTaken(value)) {
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deadBlocks.Add(block.FallThrough);
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block.replaceLastInstrsWithBranch(2, block.Targets[0]);
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}
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else {
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deadBlocks.Add(block.Targets[0]);
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block.replaceLastInstrsWithBranch(2, block.FallThrough);
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}
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}
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}
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else {
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foreach (var source in new List<Block>(block.Sources)) {
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int count = source.Instructions.Count;
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if (count > 0 && getLdcValue(source.Instructions, count - 1, ref value)) {
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removed = true;
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if (isTaken(value))
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source.replaceLastNonBranchWithBranch(1, block.Targets[0]);
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else
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source.replaceLastNonBranchWithBranch(1, block.FallThrough);
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}
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}
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deadBlocks.Add(block);
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}
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}
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scopeBlock.removeDeadBlocks(deadBlocks);
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return removed;
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}
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bool getLdcValue(IList<Instr> instrs, int i, ref int value) {
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var instr = instrs[i];
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if (instr.OpCode != OpCodes.Dup)
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return scopeBlock.getLdcValue(instr, out value);
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if (i == 0)
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return false;
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return scopeBlock.getLdcValue(instrs[i - 1], out value);
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}
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}
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class BrFalseDeobfuscator : CondBranchDeobfuscator {
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public BrFalseDeobfuscator(ScopeBlock scopeBlock, IEnumerable<Block> blocks)
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: base(scopeBlock, blocks) {
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}
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protected override bool isTaken(int value) {
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return value == 0;
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}
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}
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class BrTrueDeobfuscator : CondBranchDeobfuscator {
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public BrTrueDeobfuscator(ScopeBlock scopeBlock, IEnumerable<Block> blocks)
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: base(scopeBlock, blocks) {
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}
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protected override bool isTaken(int value) {
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return value != 0;
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}
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}
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}
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