Add constant folding

blocks/blocks.csproj

@@ -40,6 +40,7 @@
     <Compile Include="cflow\BlockCflowDeobfuscator.cs" />
     <Compile Include="cflow\CflowDeobfuscator.cs" />
     <Compile Include="cflow\CflowUtils.cs" />
+    <Compile Include="cflow\ConstantsFolder.cs" />
     <Compile Include="cflow\DeadCodeRemover.cs" />
     <Compile Include="cflow\DeadStoreRemover.cs" />
     <Compile Include="cflow\ICflowDeobfuscator.cs" />

blocks/cflow/BlocksCflowDeobfuscator.cs

@@ -31,6 +31,7 @@ namespace de4dot.blocks.cflow {
 		DeadStoreRemover deadStoreRemover = new DeadStoreRemover();
 		StLdlocFixer stLdlocFixer = new StLdlocFixer();
 		MethodCallInliner methodCallInliner = new MethodCallInliner();
+		ConstantsFolder constantsFolder = new ConstantsFolder();
 
 		public bool InlineMethods { get; set; }
 		public bool InlineInstanceMethods { get; set; }
@@ -77,6 +78,11 @@ namespace de4dot.blocks.cflow {
 				deadCodeRemover.init(allBlocks);
 				changed |= deadCodeRemover.remove();
 
+				if (!changed) {
+					constantsFolder.init(blocks, allBlocks);
+					changed |= constantsFolder.deobfuscate();
+				}
+
 				if (!changed) {
 					stLdlocFixer.init(allBlocks, blocks.Locals);
 					changed |= stLdlocFixer.fix();

blocks/cflow/ConstantsFolder.cs

@@ -0,0 +1,107 @@
+/*
+    Copyright (C) 2011 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 <http://www.gnu.org/licenses/>.
+*/
+
+using System.Collections.Generic;
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+using de4dot.blocks;
+
+namespace de4dot.blocks.cflow {
+	// Very simple constants folder which is all that's needed at the moment
+	class ConstantsFolder {
+		List<Block> allBlocks;
+		Blocks blocks;
+		InstructionEmulator instructionEmulator = new InstructionEmulator();
+		List<ParameterDefinition> args;
+
+		public void init(Blocks blocks, List<Block> allBlocks) {
+			this.blocks = blocks;
+			this.allBlocks = allBlocks;
+			args = DotNetUtils.getParameters(blocks.Method);
+		}
+
+		public bool deobfuscate() {
+			bool changed = false;
+			foreach (var block in allBlocks) {
+				instructionEmulator.init(blocks.Method.HasThis, false, blocks.Method.Parameters, blocks.Locals);
+				var instrs = block.Instructions;
+				for (int i = 0; i < instrs.Count; i++) {
+					var instr = instrs[i];
+
+					switch (instr.OpCode.Code) {
+					case Code.Ldarg:
+					case Code.Ldarg_0:
+					case Code.Ldarg_1:
+					case Code.Ldarg_2:
+					case Code.Ldarg_3:
+					case Code.Ldarg_S:
+						changed |= fixLoadInstruction(block, i, instructionEmulator.getArg(DotNetUtils.getParameter(args, blocks.Method, instr.Instruction)));
+						break;
+
+					case Code.Ldloc:
+					case Code.Ldloc_0:
+					case Code.Ldloc_1:
+					case Code.Ldloc_2:
+					case Code.Ldloc_3:
+					case Code.Ldloc_S:
+						changed |= fixLoadInstruction(block, i, instructionEmulator.getLocal(DotNetUtils.getLocalVar(blocks.Locals, instr.Instruction)));
+						break;
+
+					case Code.Ldarga:
+					case Code.Ldarga_S:
+						instructionEmulator.makeArgUnknown((ParameterDefinition)instr.Operand);
+						break;
+
+					case Code.Ldloca:
+					case Code.Ldloca_S:
+						instructionEmulator.makeLocalUnknown((VariableDefinition)instr.Operand);
+						break;
+					}
+
+					try {
+						instructionEmulator.emulate(instr.Instruction);
+					}
+					catch (System.NullReferenceException) {
+						// Here if eg. invalid metadata token in a call instruction (operand is null)
+						break;
+					}
+				}
+			}
+			return changed;
+		}
+
+		bool fixLoadInstruction(Block block, int index, Value value) {
+			if (value.isInt32()) {
+				var intValue = (Int32Value)value;
+				if (!intValue.allBitsValid())
+					return false;
+				block.Instructions[index] = new Instr(DotNetUtils.createLdci4(intValue.value));
+				return true;
+			}
+			else if (value.isInt64()) {
+				var intValue = (Int64Value)value;
+				if (!intValue.allBitsValid())
+					return false;
+				block.Instructions[index] = new Instr(Instruction.Create(OpCodes.Ldc_I8, intValue.value));
+				return true;
+			}
+			return false;
+		}
+	}
+}