obfuz/Editor/ObfusPasses/EvalStackObfus/EvalStackObfusPass.cs

using dnlib.DotNet;
using dnlib.DotNet.Emit;
using Obfuz.Data;
using Obfuz.Emit;
using Obfuz.Settings;
using Obfuz.Utils;
using System.Collections.Generic;

namespace Obfuz.ObfusPasses.EvalStackObfus
{
    class ObfusMethodContext
    {
        public MethodDef method;
        public EvalStackCalculator evalStackCalculator;
        public LocalVariableAllocator localVariableAllocator;
        public IRandom localRandom;
        public EncryptionScopeInfo encryptionScope;
        public DefaultMetadataImporter importer;
        public ModuleConstFieldAllocator constFieldAllocator;
        public float obfuscationPercentage;
    }

    internal class EvalStackObfusPass : ObfuscationMethodPassBase
    {
        private readonly EvalStackObfuscationSettingsFacade _settings;

        private IObfuscationPolicy _obfuscationPolicy;
        private IObfuscator _obfuscator;

        public EvalStackObfusPass(EvalStackObfuscationSettingsFacade settings)
        {
            _settings = settings;
            _obfuscator = new DefaultObfuscator();
        }

        public override ObfuscationPassType Type => ObfuscationPassType.EvalStackObfus;

        public override void Start()
        {
            ObfuscationPassContext ctx = ObfuscationPassContext.Current;
            _obfuscationPolicy = new ConfigurableObfuscationPolicy(
                ctx.coreSettings.assembliesToObfuscate,
                _settings.ruleFiles);
        }

        public override void Stop()
        {

        }

        protected override bool NeedObfuscateMethod(MethodDef method)
        {
            return _obfuscationPolicy.NeedObfuscate(method);
        }

        protected bool TryObfuscateInstruction(Instruction inst, EvalDataType dataType, List<Instruction> outputInstructions, ObfusMethodContext ctx)
        {
            switch (dataType)
            {
                case EvalDataType.Int32: return _obfuscator.ObfuscateInt(inst, outputInstructions, ctx);
                case EvalDataType.Int64: return _obfuscator.ObfuscateLong(inst, outputInstructions, ctx);
                case EvalDataType.Float: return _obfuscator.ObfuscateFloat(inst, outputInstructions, ctx);
                case EvalDataType.Double: return _obfuscator.ObfuscateDouble(inst, outputInstructions, ctx);
                default: return false;
            }
        }

        protected override void ObfuscateData(MethodDef method)
        {
            //Debug.Log($"Obfuscating method: {method.FullName} with EvalStackObfusPass");
            IList<Instruction> instructions = method.Body.Instructions;
            var outputInstructions = new List<Instruction>();
            var totalFinalInstructions = new List<Instruction>();

            ObfuscationPassContext ctx = ObfuscationPassContext.Current;
            var calc = new EvalStackCalculator(method);
            var encryptionScope = ctx.encryptionScopeProvider.GetScope(method.Module);
            var ruleData = _obfuscationPolicy.GetObfuscationRuleData(method);
            var localRandom = encryptionScope.localRandomCreator(MethodEqualityComparer.CompareDeclaringTypes.GetHashCode(method));
            var obfusMethodCtx = new ObfusMethodContext
            {
                method = method,
                evalStackCalculator = calc,
                localVariableAllocator = new LocalVariableAllocator(method),
                encryptionScope = encryptionScope,
                constFieldAllocator = ctx.constFieldAllocator.GetModuleAllocator(method.Module),
                localRandom = localRandom,
                importer = ctx.moduleEntityManager.GetDefaultModuleMetadataImporter(method.Module, ctx.encryptionScopeProvider),
                obfuscationPercentage = ruleData.obfuscationPercentage,
            };
            for (int i = 0; i < instructions.Count; i++)
            {
                Instruction inst = instructions[i];
                totalFinalInstructions.Add(inst);
                if (calc.TryGetPushResult(inst, out EvalDataType dataType) && localRandom.NextInPercentage(ruleData.obfuscationPercentage))
                {
                    outputInstructions.Clear();
                    if (TryObfuscateInstruction(inst, dataType, outputInstructions, obfusMethodCtx))
                    {
                        totalFinalInstructions.AddRange(outputInstructions);
                    }
                }
            }

            instructions.Clear();
            foreach (var obInst in totalFinalInstructions)
            {
                instructions.Add(obInst);
            }
        }
    }
}